Optical recording medium having auxiliary information and reference clock

ABSTRACT

An information recording medium is composed of a substrate having a microscopic pattern constituted by a continuous substrate of grooves formed with a groove portion and a land portion alternately, a recording layer, and a light transmitting layer. The microscopic pattern is formed with satisfying a relation of P≦λ/NA, wherein P is a pitch of the land portion or the groove portion, λ is a wavelength of reproducing light, and NA is a numerical aperture of an objective lens. The land portion is formed with wobbling so as to be parallel with each other for both sidewalls of the land portion. Auxiliary information and a reference clock are recorded alternately. Information is recorded in the recording layer corresponding to a land portion by either one change of reflectivity difference and refractive index difference in the recording layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending application Ser. No.13,459,735, filed Apr. 30, 2012 (allowed), which is a Continuation ofapplication Ser. No. 13/010,212, filed Jan. 20, 2011 (abandoned), whichis a Continuation of application Ser. No. 12/652,809, filed on Jan. 6,2010 (now U.S. Pat. No. 7,907,504), which is a Continuation ofapplication Ser. No. 11/969,503, filed on Jan. 4, 2008 (now U.S. Pat.No. 7,668,072), which is a Continuation of application Ser. No.11/620,150, filed on Jan. 5, 2007 (now U.S. Pat. No. 7,336,595), whichis a Continuation of application Ser. No. 10/419,149, filed on Apr. 21,2003 (now U.S. Pat. No. 7,177,162), and for which priority is claimedunder 35 U.S.C. §120; and this application claims priority ofApplication No. 2002-117555 filed in Japan on Apr. 19, 2002 under 35U.S.C. §119; this application also claims priority of Application No.2002-141286 filed in Japan on May 16, 2002 under 35 U.S.C. §119; thisapplication also claims priority of Application No. 2002-160129 filed inJapan on May 31, 2002 under 35 U.S.C. §119; this application also claimspriority of Application No. 2002-123612 filed in Japan on Apr. 25, 2002under 35 U.S.C. §119; and this application claims priority ofApplication No. 2002-148781 filed in Japan on May 23, 2002 under 35U.S.C. §119; the entire contents of all are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information recording medium that isparticularly used for recording information and a reproducing apparatusfor reading out information recorded in the information recording mediumwith making the information recording medium move relatively,particularly, relates to an information recording medium for recordingand/or reproducing information optically and a reproducing apparatusthereof.

2. Description of the Related Art

Until now, there existed a system used for reading out information froman information recording medium while the information recording mediumis made relatively move. In order to reproduce the system, such a methodas optical, magnetic or capacitance is utilized. A system for recordingand/or reproducing information by the optical method has been mostpopular in daily life. In the case of a read-only type informationrecording medium in disciform, which is reproduced by a light beamhaving a wavelength of 650 nm, for example, such a medium in disciformas a DVD video disc pre-recorded with picture image information, aDVD-ROM disc that is pre-recorded with a program or like, a DVD audiodisc, or an SACD (Super Audio CD) disc that is pre-recorded with musicalinformation is popularly known.

In the case of a recording and reproducing type information recordingmedium, there existed a DVD RAM disc utilizing a phase change effect, anASMO (Advanced Storage Magneto-Optical) disc and an iD (intelligentimage disc) utilizing a magneto-optical effect.

On the other hand, in order to increase recording density, such a studyas shortening a wavelength of laser beam so as to realize emission ofviolaceous light has been continued. A second harmonic oscillatingelement or a semiconductor light emitting element of gallium nitridesystem compound, which was invented recently, emits light having awavelength λ in the neighborhood of 350 nm to 450 nm. Consequently, theyare possible to be an important light emitting element, which increasesrecording density drastically.

Further, a design of objective lens complying with such a wavelength hasbeen advanced. Particularly, an objective lens having an NA (numericalaperture) utilized for a DVD disc, that is, an NA of exceeding 0.6 andmore than 0.7 is being developed.

As mentioned above, a reproducing apparatus for information recordingmedium that is equipped with a light emitting element of whichwavelength λ is reduced down to 350 nm to 450 nm and equipped with anobjective lens of which an NA is more than 0.7 is being developed. Byusing these technologies, it can be expected that an optical discsystem, which surpasses recording capacity of current DVD disc furthermore, will be developed.

Further, it is also desired that an information recording medium havinghigher recording density, which is designed on the basis of a violaceouslaser beam and a higher NA, is developed.

On the other hand, a recent recording and reproducing type disc adopts amicroscopic configuration, namely the land-groove system. With referringto FIGS. 41 and 42, an information recording medium designed for ahigher NA recording and reproducing system is explained.

FIG. 41 is a cross sectional view of a conventional informationrecording medium adopting the microscopic configuration that is calledthe land-groove system according to the prior art.

FIG. 42 is an enlarged plan view of the information recording mediumshown in FIG. 41 showing the horizontal configuration of the informationrecording medium according to the prior art.

As shown in FIG. 41, an information recording medium 100 is composed ofa recording layer 120 and a light transmitting layer 110 that aresequentially laminated on a substrate 130. A microscopic pattern 131 isformed on the substrate 130. The recording layer 120 is formed directlyon the surface of the microscopic pattern 131. The microscopic pattern131 is composed of a plural of land portions “La” and “Lb” (hereinaftergenerically referred to as land portion “L”) and a plural of grooveportions “Ga” to “Gc” (hereinafter generically referred to as grooveportion “G”). Macroscopically, the configuration corresponds to that themicroscopic pattern 131 is constituted by a continuous groove composedof the land portion “L” and another continuous groove composed of thegroove portion “G”.

Further, as shown in FIG. 42, a record mark “M” is formed in both thegrooves composed of the land portion “L” and the groove portion “G”respectively when recording.

With paying attention to the dimensions of the microscopic pattern 131,while a shortest distance between the groove portions “Ga” and “Gb” isassumed to be a pitch “P0” (another shortest distance between the landportions “La” and “Lb” is also the pitch “P0”), the microscopic pattern131 is formed so as to satisfy a relation of P0>S0, wherein “S0” is aspot diameter of reproducing light beam.

Hereupon, the spot diameter “S0” is calculated by a wavelength λ oflaser beam for reproducing and an NA of objective lens such as S0=λ/NA.In other words, the pitch “P0” is designed so as to satisfy a relationof P0>λ/NA.

In the case of the information recording medium 100, a light beam forrecording (recording light) is irradiated on the light transmittinglayer 110 and a record mark “M” is formed on both the land portion “L”and the groove portion “G” of the recording layer 120.

Further, a light beam for reproducing (reproducing light) is irradiatedon the substrate 130 or the light transmitting layer 110 and reflectedby the recording layer 120, and then the reflected reproducing light ispicked up for reproducing.

Inventors of the present invention have actually manufactured aninformation recording medium 100 as an experiment, and experimentallyrecorded and reproduced the information recording medium 100. Theinventors founded a problem such that a cross erase phenomenon wasextremely noticeable. The cross erase phenomenon is a phenomenon suchthat information is recorded with being superimposed on a signalpreviously recorded in a groove portion “G”, for example, when recordingthe information in a land portion “L”. In other words, it is such aphenomenon that information previously recorded in a groove portion “G”is erased by recording another information in a land portion “L”.

Further, this phenomenon can also be noticeable in a reverse case, thatis, the cross erase phenomenon is also recognized if previously recordedinformation in a land portion “L” is observed when recording informationin a groove portion “G”. If such a cross erase phenomenon occurs, asmentioned above, information recorded in an adjacent groove is damaged.In case of an information system having larger capacity, an amount oflost information becomes excessively large. Consequently, affection to auser is enormous.

Consequently, it is considered for such an information recording medium100 that information shall be recorded only in either land portion “L”or groove portion “G”. However, there is existed a problem such thatrecording capacity of an information recording medium will decrease anda merit of the information recording medium having a potential ofrecording in higher density will decline if such an informationrecording method is conducted.

SUMMARY OF THE INVENTION

Accordingly, in consideration of the above-mentioned problems of theprior art, an object of the present invention is to provide aninformation recording medium that is reduced in cross erase and can berecorded in higher density, and an reproducing apparatus for reproducinginformation recorded in the information recording medium with making theinformation recording medium move relatively.

In order to achieve the above object, the present invention provides,according to an aspect thereof, an information recording medium at leastcomprising: a substrate having a microscopic pattern constituted by acontinuous substrate of grooves formed with a groove portion and a landportion alternately; a recording layer formed on the microscopic patternfor recording information; and a light transmitting layer formed on therecording layer, the information recording medium is furthercharacterized in that the microscopic pattern is formed with satisfyinga relation of P≦λ/NA, wherein P is a pitch of the land portion or thegroove portion, λ is a wavelength of reproducing light for reproducingthe recording layer, and NA is a numerical aperture of an objectivelens, and that the land portion is formed with wobbling so as to beparallel with each other for both sidewalls of the land portion, andthat an auxiliary information based on data used supplementally whenrecording the information and a reference clock based on a clock usedfor controlling a recording speed when recording the information isrecorded alternately and continuously.

According to another aspect of the present invention, there provide areproducing apparatus for reproducing a recording layer of aninformation recording medium comprising: a substrate having amicroscopic pattern constituted by a continuous substrate of groovesformed with a groove portion and a land portion alternately; therecording layer formed on the microscopic pattern for recordinginformation; and a light transmitting layer formed on the recordinglayer, the information recording medium is further characterized in thatthe microscopic pattern is formed with satisfying a relation of P≦λ/NA,wherein P is a pitch of the land portion or the groove portion, λ is awavelength of reproducing light for reproducing the recording layer, andNA is a numerical aperture of an objective lens, and that the landportion is formed with wobbling so as to be parallel with each other forboth sidewalls of the land portion, and that an auxiliary informationbased on data used supplementally when recording the information and areference clock based on a clock used for controlling a recording speedwhen recording the information is recorded alternately and continuously,the reproducing apparatus comprising: a light emitting element foremitting reproducing light having a wavelength λ of 350 nm to 450 nm anda noise of less than RIN (Relative Intensity Noise) −125 dB/Hz; areproducing means equipped with an objective lens having a numericalaperture NA of 0.75 to 0.9; and a control means for controlling thereproducing means to irradiate the reproducing light only on the landportion for reproducing.

Other object and further features of the present invention will beapparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross sectional view of an information recording mediumaccording to a first embodiment of the present invention.

FIG. 2 is an enlarged plan view of a microscopic pattern of theinformation recording medium shown in FIG. 1.

FIG. 3 is another enlarged plan view of a microscopic pattern of theinformation recording medium shown in FIG. 1 exhibiting a state of beingrecorded.

FIG. 4 is a cross sectional view of the information recording mediumshown in FIG. 1 exhibiting a state of reproducing or recording arecording layer of the information recording medium.

FIG. 5 is an enlarged plan view showing an auxiliary information areaand a reference clock area in the information recording medium accordingto the first embodiment of the present invention.

FIG. 6 is an enlarged plan view of the information recording mediumaccording to the first embodiment of the present invention wheninformation is recorded in the information recording medium through theCLV (Constant Linear Velocity) recording method.

FIG. 7 is an enlarged plan view of the information recording mediumaccording to the first embodiment of the present invention wheninformation is recorded on the information recording medium through theCAV (Constant Angular Velocity) recording method.

FIG. 8 is an enlarged plan view of the information recording medium indisciform according to the first embodiment of the present inventionwhen information is recorded in the information recording medium throughthe CLV recording method.

FIG. 9 is an enlarged plan view of the information recording medium indisciform according to the first embodiment of the present inventionwhen information is recorded on the information recording medium throughthe CLV recording method and further the information is recorded on aland portion.

FIG. 10 is an enlarged plan view of a photo-detector mounted on anapparatus for reproducing an information recording medium according tothe present invention showing a state of dividing the photo-detectorinto four.

FIG. 11 is a first example showing a distributed recording of auxiliaryinformation.

FIG. 12 is a second example showing a distributed recording of auxiliaryinformation.

FIG. 13 is a third example showing a distributed recording of auxiliaryinformation.

FIG. 14 is a fourth example showing a distributed recording of auxiliaryinformation.

FIG. 15 is a table exhibiting data change before and after modulating abase-band.

FIG. 16 is a table exhibiting an example of actual data change beforeand after modulating a base-band.

FIG. 17 shows a first example of an amplitude-shift keying modulationwaveform according to the present invention.

FIG. 18 shows a second example of an amplitude-shift keying modulationwaveform according to the present invention.

FIG. 19 shows a third example of an amplitude-shift keying modulationwaveform according to the present invention.

FIG. 20 shows a first example of a frequency-shift keying modulationwaveform according to the present invention.

FIG. 21 shows a second example of a frequency-shift keying modulationwaveform according to the present invention.

FIG. 22 shows a third example of a frequency-shift keying modulationwaveform according to the present invention.

FIG. 23 shows a first example of a phase-shift keying modulationwaveform according to the present invention.

FIG. 24 shows a second example of a phase-shift keying modulationwaveform according to the present invention.

FIG. 25 shows a third example of a phase-shift keying modulationwaveform according to the present invention.

FIG. 26 shows a first example of a shape of the information recordingmedium according to the present invention.

FIG. 27 shows a second example of a shape of the information recordingmedium according to the present invention.

FIG. 28 shows a third example of a shape of the information recordingmedium according to the present invention.

FIG. 29 is a cross sectional view of an information recording mediumaccording to a second embodiment of the present invention.

FIG. 30 is a cross sectional view of an information recording mediumaccording to a third embodiment of the present invention.

FIG. 31 is a cross sectional view of an information recording mediumaccording to a fourth embodiment four of the present invention.

FIG. 32 is a cross sectional view of an information recording mediumaccording to a fifth embodiment of the present invention.

FIG. 33 is a block diagram of a first reproducing apparatus of aninformation recording medium according to an embodiment of the presentinvention.

FIG. 34 is a block diagram of a second reproducing apparatus of aninformation recording medium according to an embodiment of the presentinvention.

FIG. 35 is a flow chart showing a reproducing method of an informationrecording medium according to an embodiment of the present invention.

FIG. 36 is a block diagram of a recording apparatus of an informationrecording medium according to an embodiment of the present invention.

FIG. 37 is a flow chart showing a recording method of an informationrecording medium according to an embodiment of the present invention

FIG. 38 is a graph exhibiting a relation between reflectivity and errorrate.

FIG. 39 is a chart exhibiting reflectivity and reproductioncharacteristics of embodiments 1 through 7 and comparative examples 1and 2.

FIG. 40 is a graph exhibiting a relation between modulated amplitude anderror rate.

FIG. 41 is a cross sectional view of a conventional informationrecording medium according to the prior art.

FIG. 42 is an enlarged plan view of the information recording mediumshown in FIG. 41.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

With referring to FIG. 1, a basic configuration of an informationrecording medium according to the present invention will be explained.An information recording medium according to a first embodiment of thepresent invention is such an information recording medium that at leastone of recording and reproducing is conducted through an optical method.Actually, it is such an information recording medium as a phase changerecording type information recording medium, a dye type informationrecording medium, a magneto-optical type information recording medium ora light assist magnetic type information recording medium.

FIG. 1 is a cross sectional view of an information recording mediumaccording to a first embodiment of the present invention. In FIG. 1, aninformation recording medium 1 according to the present invention is atleast composed of a light transmitting layer 11, a recording layer 12,and a substrate 13 formed with a microscopic pattern 20. They are formedsequentially on the substrate 13. Unevenness of the microscopic pattern20 forms a shape of continuous substance of approximately parallelgrooves, wherein a symbol sign 21 is a microscopic pattern that isrecorded with a record mark “M” as shown in FIG. 3.

Further, a shape of the information recording medium 1 can be applicablein any shape such as disciform, card and tape even in circular,rectangular or oval shape. The information recording medium 1 can alsobe acceptable although it is perforated.

Furthermore, a light beam for reproducing (reproducing light) orrecording (recording light) is irradiated on the light transmittinglayer 11.

The substrate 13, the recording layer 12, and the light transmittinglayer 11 are detailed first. The substrate 13 is a base substance havinga function of sustaining mechanically the recording layer 12 and thelight transmitting layer 11 sequentially laminated thereon. With respectto a material for the substrate 13, any of synthetic resin, ceramic andmetal is used. A typical example of synthetic resin is various kinds ofthermoplastic resins and thermosetting resins such as polycarbonate,polymethyle methacrylate, polystyrene, copolymer of polycarbonate andpolystyrene, polyvinyl chloride, alicyclic polyolefin and polymethylepentene, and various kinds of energy ray curable resins such as UV raycurable resins, visible radiation curable resins and electron beamcurable resins. They can be preferably used.

Further, it is also acceptable that these synthetic resins are mixedwith metal powder or ceramic powder.

With respect to a typical example of the ceramic, soda lime glass, sodaaluminosilicate glass, borosilicate glass or silica glass can be used.With respect to a typical example of the metal, a metal plate such asaluminum having no transparency can be used. A thickness of thesubstrate 13 is suitable to be within a range of 0.3 mm to 3 mm,desirably 0.5 mm to 2 mm due to necessity of supporting mechanically theinformation recording medium 1 totally. In case that the informationrecording medium 1 is in disciform, the thickness of the substrate 13 isdesirable to be designed such that the total thickness of theinformation recording medium 1 including the substrate 13, the recordinglayer 12, and the light transmitting layer 11 becomes 1.2 mm, for thepurpose of interchangeability with a conventional optical disc.

The recording layer 12 is a thin film layer that has a function ofreading out information, recording or rewriting information. Therecording layer 12 is formed with the microscopic pattern 20 that isconstituted by a plurality of land portions “L1” through “L4”(hereinafter generically referred to as land portion “L”) and aplurality of groove portions “G1” through “G5” (hereinafter genericallyreferred to as groove portion “G”) respectively. Information is recordedon either one of a land portion “L” and a groove portion “G” as a recordmark “M”. With respect to a material for the recording layer 12, amaterial that is represented by a phase-change material of whichreflectivity or refractive index changes in a process of before andafter recording or both of reflectivity and refractive index change in aprocess of before and after recording, a dye material of whichrefractive index or a depth changes in a process of before and afterrecording or both of refractive index and depth change in a process ofbefore and after recording, or a material represented by amagneto-optical material, which produces a change of Kerr rotation anglein a process of before and after recording, can be used.

With respect to an actual example of phase change material, alloyscomposed of an element such as indium (In), antimony (Sb), tellurium(Te), selenium (Se), germanium (Ge), bismuth (Bi), vanadium (V), gallium(Ga), platinum (Pt), gold (Au), silver (Ag), copper (Cu), aluminum (Al),silicon (Si), palladium (Pd), tin (Sn) and arsenic (As) are used,wherein an alloy includes a compound such as oxide, nitride, carbide,sulfide and fluoride. Particularly, alloys composed of a system such asGe—Sb—Te system, Ag—In—Te—Sb system, Cu—Al—Sb—Te system and Ag—Al—Sb—Tesystem are suitable for the recording layers 12. These alloys cancontain one or more elements as a micro additive element within a rangeof more than 0.01 atomic % to less than 10 atomic % in total. Such amicro additive element is selected out of Cu, Ba, Co, Cr, Ni, Pt, Si,Sr, Au, Cd, Li, Mo, Mn, Zn, Fe, Pb, Na, Cs, Ga, Pd, Bi, Sn, Ti, V, Ge,Se, S, As, Tl and In.

With respect to compositions of each element, for example, there isexisted Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, Ge₈Sb₆₉Te₂₃, Ge₈Sb₇₄Te₁₈, Ge₅Sb₇₁Te₂₄,Ge₅Sb₇₆Te₁₉, Ge₁₀Sb₆₈Te₂₂ and Ge₁₀Sb₇₂Te₁₈ as for the Ge—Sb—Te systemand a system adding a metal such as Sn and In to the Ge—Sb—Te system asfor the Ge—Sb—Te system.

Further, as for the Ag—In—Sb—Te system, there is existed Ag₄In₄Sb₆₆Te₂₆,Ag₄In₄Sb₆₄Te₂₈, Ag₂In₆Sb₆₄Te₂₈, Ag₃In₅Sb₆₄Te₂₈, Ag₂In₆Sb₆₆Te₂₆, and asystem adding a metal or semiconductor such as Cu, Fe and Ge to theAg—In—Sb—Te system.

With respect to an actual example of magneto-optical material, alloyscomposed of an element such as terbium, cobalt, iron, gadolinium,chromium, neodymium, dysprosium, bismuth, palladium, samarium, holmium,praseodymium, manganese, titanium, erbium, ytterbium, lutetium and tincan be used, wherein an alloy includes a compound such as oxide,nitride, carbide, sulfide and fluoride. Particularly, constituting analloy of a transition metal, which is represented by TbFeCo, GdFeCo andDyFeCo, with rare earth element is preferable. Further, the recordinglayer 12 can be constituted by using an alternate lamination layer ofcobalt and platinum.

With respect to an actual example of dye material, cyanine dye,phthalocyanine dye, naphthalocyanine dye, azo dye, naphthoquinone dye,fulgide dye, polymethine dye, acridine dye, and porphyrin dye can beused.

With respect to a method of forming the recording layers 12, a filmforming method such as a vapor phase film forming method and a liquidphase film forming method can be used. As a typical example of the vaporphase film forming method, such methods as vacuum deposition of resisterheating type or electron beam type, direct current sputtering, highfrequency sputtering, reactive sputtering, ion beam sputtering, ionplating and chemical vapor deposition (CVD) can be used.

Further, with respect to a typical example of the liquid phase filmforming method, there is existed a spin coating method and a dipping anddrawing up method.

The light transmitting layer 10 is composed of a material havingfunction of conducting converged reproducing light to the recordinglayer 12 while keeping the converged reproducing light in less opticaldistortion. A material having transmittance of more than 70%, forexample, at a reproduction wavelength λ, desirably more than 80% can besuitably used for the light transmitting layer 11.

It is essential for the light transmitting layer 11 to be less opticalanisotropy. In order to suppress reduction of reproducing light,actually, a material having birefringence of less than ±100 nm,preferably ±50 nm by 90-degree (vertical) incident double paths is usedfor the light transmitting layer 11.

With respect to a material having such a birefringence characteristic, asynthetic resin such as polycarbonate, polymethyle methacrylate,cellulose triacetate, cellulose diacetate, polystyrene, copolymer ofpolycarbonate and polystyrene, polyvinyl chloride, alicyclic polyolefinand polymethyle pentene can be used for the light transmitting layer 11.

The light transmitting layer 11 can be provided with a function ofprotecting the recording layer 12 mechanically and chemically. Withrespect to a material having such a function, a material having higherstiffness can be used for the light transmitting layer 11. For example,transparent ceramics (such as soda lime glass, soda aluminosilicateglass, borosilicate glass, and silica glass), thermosetting resin,energy ray curable resin (such as ultraviolet rays curable resin,visible radiation curable resin and electron beam curable resin),moisture curable resin and two-part liquid mixture curable resin arepreferably used for the light transmitting layer 11 having higherstiffness.

Further, a thickness of the light transmitting layer 11 is desirable tobe less than 0.4 mm in view of suppressing aberration when theinformation recording medium 1 is inclined.

Furthermore, in view of preventing the recording layer 12 from beingscratched, the thickness of the light transmitting layer 11 is desirableto be more than 0.05 mm. In other words, the desirable thickness of thelight transmitting layer 11 is within a range of 0.05 mm to 0.4 mm. Moredesirably, the thickness is within a range of 0.06 mm to 0.12 mm.

More, scattering of thickness in a single plain is desirable to be±0.003 mm maximum in view of spherical aberration, because an NA ofobjective lens is relatively large. Particularly, in case that an NA ofthe objective lens is more than 0.85, the scattering of thickness in asingle plain is desirable to be less than ±0.002 mm.

Moreover, in case that an NA of the objective lens is 0.9, thescattering of thickness in a single plain is desirable to be less than±0.001 mm.

With referring to FIG. 2, the microscopic pattern 20 that is one ofmajor features of the present invention is explained next. As mentionedabove, microscopically, the microscopic pattern 20 is composed of acontinuous substance of approximately parallel grooves. However,macroscopically, the continuous substance can be in a shape of not onlylinear but also coaxial or spiral.

FIG. 2 is an enlarged plan view of a microscopic pattern of theinformation recording medium shown in FIG. 1. In FIG. 2, symbol signs“P” and “S” are a pitch between adjoining two groove portions “G2” and“G3” and a spot diameter of reproducing light beam respectively. Asshown in FIG. 2, a land portion “L” of the microscopic pattern 20corresponds to the land (raised) portion “L” shown in FIG. 1 and agroove portion “G” of the microscopic pattern 20 corresponds to thegroove (recessed) portion “G” shown in FIG. 1.

Further, the land portion “L” and the groove portion “G” can be wobbled,will be mentioned later. However, centerlines of the land portion “L”and the groove portion “G” are formed in parallel to each other.

In case that a user records data in the information recording medium 1,the data are recorded only on either one of the land portion “L” and thegroove portion “G”. Accurately, the data are recorded on a portioncorresponding to either one of the land portion “L” and the grooveportion “G” in the recording layer 12. Selecting either the land portion“L” or the groove portion “G” is arbitrary. However, it is desirable forselecting the land portion “L” or the groove portion “G” to maintain atleast a same selection result of either the land portion “L” or thegroove portion “G” even in any place in the recording layer 12. In caseof recording on different portions by a place, it is hard to reproducecontinuously and resulted in degrading a recording capacitysubstantially.

In FIG. 2 and succeeding drawings FIGS. 3 to 9, a width of the landportion “L” and a width of the groove portion “G” is illustrated indifferent width in each drawing. However, it is understood that thewidth is not limited to one specific width.

FIG. 3 is a plan view of a microscopic pattern of the informationrecording medium 1 shown in FIG. 1 exhibiting an example of recordingthat is conducted only on land portions “L” of the recording layer 12.As shown in FIG. 3, a record mark “M” is recorded only on the landportions “L1” through “L4” not on the groove portions “G1” through “G5”,which constitute the microscopic pattern 21. The record mark “M” isrecorded by a mark position recording method or a mark edge recordingmethod.

A signal, which is used for recording, is a modulation signal that is aso-called (d, k) code, which is defined as that a minimum mark length is“d+1” and a maximum mark length is “k+1”, wherein either a fixed lengthcode or a variable length code can be applied for a (d, k) modulationsignal. Actually, with defining that a minimum mark length is 2T, a (d,k) modulation such as (1, 7) modulation, 17PP modulation, DRLmodulation, (1, 8) modulation and (1, 9) modulation can be used.

A typical example representing the (1, 7) modulation of the fixed lengthcode is the “D1, 7” modulation (that is disclosed in the Japanese PatentApplication No. 2001-80205 in the name of Victor company of Japan,Limited). The “D1, 7” modulation can be replaced by the (1, 7)modulation or the (1, 9) modulation, which is based on the “D4, 6”modulation of the fixed length code (that is disclosed in the JapanesePatent Application Laid-open Publication No. 2000-332613). The 17PPmodulation is one of the (1, 7) modulation of the variable length codeand disclosed in the Japanese Patent Application Laid-open PublicationNo. 11-346154/1999.

Further, the (2, 7) modulation and the (2, 8) modulation, which are thevariable length code with defining the minimum mark length as 3T, theEFM modulation, the EFM plus modulation, and the “D8-15” modulation(that is disclosed in the Japanese Patent Application Laid-openPublication No. 2000-286709) as the (2, 10) modulation of the fixedlength code can be used.

Furthermore, a modulation system, which defines the minimum mark lengthas 4T such as the (3, 17) modulation, and another modulation system,which defines the minimum mark length as 5T such as the (4, 21)modulation, can be used.

A groove portion “G” hereupon follows the definition shown in the Table4.4-1 described in the publication “Understanding Optical Disc Properly”(edited by the Japan Patent Office and published by the Japan Instituteof Invention and Innovation in 2000). In other words, a groove portion“G” is defined as a recessed groove previously provided spirally orcoaxially on a surface of base substance in order to form a recordingtrack.

Further, a land portion “L” also follows the definition described in thepublication. In other words, a land portion “L” is defined as a landportion previously provided spirally or coaxially on a surface of basesubstance in order to form a recording track.

Furthermore, the base substance hereupon is a name equivalent to thesubstrate 11 of the present invention.

In FIGS. 2 and 3, with defining that a distance between adjoining twogroove portions “G2” and “G3” is a pitch “P” (in the same way, adistance between adjoining two land portions “L1” and “L2” is alsodefined as the pitch “P”), the pitch “P” is designated so as to satisfya relation of P≦S, wherein “S” is a spot diameter of reproducing light.The spot diameter “S” is calculated by a wavelength λ of laser beam forreproducing and an NA of objective lens such as S=λ/NA. In other words,the pitch “P” satisfies a relation of P≦λ/NA.

In case of using a violaceous laser beam, its wavelength λ is within arange of 350 nm to 450 nm, and in case of using a high NA lens, its NAis 0.75 to 0.9. Consequently, a pitch “P” is set to be within a range of250 nm to 600 nm.

Further, in case of considering that a digital picture image of HDTV(High Definition Television) program is recorded for approximately twohours, more than 20 GB is necessary for a recording capacity.Consequently, the pitch “P” is desirable to be within a range of 250 nmto 450 nm. Particularly, in case that an NA is 0.85 to 0.9, the pitch“P” is more desirable to be 250 nm to 400 nm.

Furthermore, in case that a wavelength λ is 350 nm to 410 nm and also anNA is 0.85 to 0.9, the pitch “P” is most desirable to be 250 nm to 360nm.

A depth of groove portion “G” is preferable to be within a range of λ/8nto λ/20n, wherein “n” is a refractive index at a wavelength λ of thelight transmitting layer 11. Since a reflectivity of the recording layer12 is reduced a little due to existence of the microscopic pattern 20, adepth of groove portion “G” is desirable to be shallower. Less thanλ/10n is suitable for the depth of groove portion “G” as a limit forjitter of a reproduced signal not to be deteriorated.

Further, an output of push-pull signal increases in accordance with adepth of groove portion “G” when tracking down a land portion “L” or agroove portion “G”. Consequently, more than λ/18n is suitable for alimiting value for enabling to track. In other words, a range of λ/10nto λ/18n is suitable for a depth of groove portion “G”, and a mostsuitable range for the depth of groove portion “G” is λ/10n to λ/18n.

As mentioned above, the information recording medium 1 according to thefirst embodiment of the present invention is such an informationrecording medium that is recorded on either a groove portion “G” or aland portion “L” of the recording layer 12. Therefore, recording isconducted with keeping a distance of pitch “P” and resulted indecreasing the cross erase phenomenon.

Further, it is designed for the relation between the pitch “P” and thespot diameter “S” to be P≦S, so that recording density is prevented fromdecreasing.

A result of evaluation with respect to the cross erase phenomenon incomparison with a conventional information recording medium 100 isdepicted hereinafter. With respect to an information recording medium ofwhich recording layer 12 is formed by a phase change material, a secondtrack is recorded and reproduced, and the reproduced output is measured.Then, a first track and a third track is recorded ten times each with asignal having a frequency different from that recorded on the secondtrack, and an output from the second track is measured once again. Withdefining that an output difference between the outputs originallymeasured and secondary measured is a cross erase amount, a cross eraseamount cause by the conventional information recording medium 100 is −5dB. On the contrary, by the information recording medium 1 according tothe first embodiment of the present invention, a cross erase amount isreduced to the order of −2 dB. In other words, by using the informationrecording medium 1 according to the first embodiment of the presentinvention, a cross erase phenomenon can be improved by 3 dB incomparison with the conventional information recording medium 100.

Further, a similar evaluation is conducted to an information recordingmedium of which recording layer 12 is formed by a magneto-opticalmaterial. By the conventional information recording medium 100, anoutput decreases by 4 dB. On the contrary, by the information recordingmedium 1 according to the first embodiment of the present invention, anoutput decreases by just 1 dB. In other words, by using the informationrecording medium 1, a cross erase phenomenon is improved by up to 3 dBin comparison with the conventional information recording medium 100although a magneto-optical material is used for the informationrecording medium 1.

Furthermore, a similar evaluation is conducted to an informationrecording medium of which recording layer 12 is formed by a dyematerial. By the conventional information recording medium 100, anoutput decreases drastically by 12 dB. On the contrary, by theinformation recording medium 1, an output decreases by as low as 2 dB.In other words, by using the information recording medium 1, a crosserase phenomenon is improved by up to 10 dB in comparison with theconventional information recording medium 100 although a dye material isused for the information recording medium 1.

The information recording medium 1 according to the first embodiment ofthe present invention is such an information recording medium that isrecorded with information on either a groove portion “G” or a landportion “L” of the recording layer 12. It is studied that either portionis suitable for recording information in view of reproduction, and it isfounded that recording on a land portion “L” of the recording layer 12decreases an error rate and is excellent in a rewriting characteristic.In view of that a land portion “L” is disposed in a side closer to thelight transmitting layer 11 than a groove portion “G”, and reproducinglight and recording light is irradiated on the light transmitting layer11, it is considered that thermal flow of a material constituting therecording layers 12 is suppressed to some degree in an area of landportion “L”.

FIG. 4 is a cross sectional view of the information recording medium 1according to the first embodiment of the present invention exhibiting astate of recording and reproducing the recording layer 12. In FIG. 4, arecording apparatus and a reproducing apparatus is illustrated by anobjective lens 50 b as a representative of them. A laser beam 89 isemitted through the objective lens 50 b of the recording apparatus whenrecording. The laser beam 89 is converged selectively on a land portion“L” of the microscopic pattern 20 in the information recording medium 1with respect to the horizontal direction. As for the vertical direction,the laser beam 89 is converged selectively on the recording layer 12through the light transmitting layer 11.

Further, a record mark “M” is recorded on a portion where the laser beam89 is converged on. In other words, recording is selectively conductedto the recording layer 12 corresponding to a land portion “L”.

As mentioned above, in the case that the recording layer 12 is formed bya phase change material, the recording hereupon is conducted by changeof reflectivity, change of refractive index, or change of both of them.In the case of being formed by a magneto-optical material, the recordingis conducted by change of Kerr rotation angle.

Further, in the case of a dye material, the recording is conducted bychange of refractive index, change of depth, or change of both of them.

On the other hand, when reproducing, a laser beam 99 is emitted throughthe objective lens 50 b of the reproducing apparatus. The laser beam 99is converged selectively on a land portion “L” of the microscopicpattern 21 in the information recording medium 1 with respect to thehorizontal direction.

Further, with respect to the vertical direction, the laser beam 99 isconverged selectively on the recording layer 12 through the lighttransmitting layer 11. A record mark “M” is recorded selectively on therecording layer 12 corresponding to a land portion “L”. Consequently, arecord mark “M” can be read out from a portion where the laser beam 99is converged on.

According to the first embodiment of the present invention, as mentionedabove, the microscopic pattern 20 of the information recording medium 1is formed to be P≦λ/NA, wherein “P” is the pitch between adjoining twogroove portions “G” or land portions “L”, “λ” is a wavelength of a laserbeam for recording or reproducing, and “NA” is a numerical aperture ofan objective lens.

Further, recording is conducted to either one of a land portion “L” anda groove portion “B”. Consequently, an information recording mediumrecorded in high density can be obtained as well as reducing a crosserase phenomenon.

In addition thereto, according to the first embodiment of the presentinvention, an information recording medium that is low in error rate andexcellent in rewriting characteristic can be obtained by recordingselectively on a land portion “L”.

A method of embedding an auxiliary information such as address and areference clock, which is a second object of the information recordingmedium 1 according to the first embodiment of the present invention, isexplained hereafter. The present invention is explained by specifying anembodiment in which recording is conducted on a land portion “L”hereupon.

In case of a recording type information recording medium, it is requiredthat recording is accurately conducted in an arbitrary position, whichis requested by a user. If the recording type information recordingmedium is constituted by arranging a groove portion “G” and a landportion “L” alternatively as shown in FIG. 2, positioning based on arelative distance between a recording apparatus or reproducing apparatusand the information recording medium can only be conducted. Therefore,recording in a required position can not be conducted accurately.

Accordingly, an address information is essential to be embedded insomewhere on the microscopic pattern 20. It is considered that analternating configuration of groove portion “G” and land portion “L” asthe same configuration as a commonly known optical disc such as a CD,for example, is transported to a free plane at each certain macroscopicinterval (each interval of the order of milli) and pits having aplurality of lengths are arranged into the free plane. An addressinformation is defined by a combination of the pit length. Reading out apit in such a free plane can be conducted by reading out a depth asphase change that is the same manner as a CD, so that the reading out apit is an easy method. However, providing such a free plane as anaddress area makes losses of recording capacity expands. In view ofreliability of reading out, the loss is approximately 10% and hard to beallowed.

Furthermore, in the case of the recording type information recordingmedium, a relative speed between an information recording medium and arecording apparatus, that is, a recording speed affects a recordingdensity and besides, signal quality. Therefore, a reference clock fordesignating a recording speed correctly is essential. In case that areference clock is provided in a recording apparatus, a relative speedcan hardly be adjusted even though the relative speed is shifted byvarious conditions. Consequently, it is desirable for the referenceclock to be provided inside an information recording medium.Particularly, the information recording medium 1 is in disciform and alinear velocity changes every moment in case of a recording mode by theCLV (Constant Linear Velocity) recording method. Therefore, it isessential for the reference clock to be provided inside the informationrecording medium 1.

In order to solve the problems and satisfy the requirements mentionedabove, there provided a method for embedding an auxiliary informationand a reference clock in the information recording medium 1. Anauxiliary information hereupon is a data array that is used subsidiarilywhen recording in the recording layer 12 of the information recordingmedium 1 by a user.

Actually, an auxiliary information is composed of at least an addressinformation. An address information exhibits an address that changescontinuously by a position of the information recording medium 1 and isdata selected out from information such as absolute address allocated tothe whole area of the information recording medium 1, relative addressallocated to a partial area, track number, sector number, frame number,field number, and time information.

These address data sequentially change in the order of increment ordecrement in accordance with progress of a recording track such as aland portion “L”, for example.

It is acceptable that an address information can be accompanied by aspecific information, which is composed of a small amount of data. Aspecific information is common data in the plain of the recording layer12. Such a specific information is at least selected out from, forexample, type of an information recording medium, size of theinformation recording medium, estimated recording capacity of theinformation recording medium, estimated recording linear density of theinformation recording medium, estimated recording linear velocity of theinformation recording medium, track pitch of the information recordingmedium, recording strategic information such as peak power, bottompower, erase power, and pulse period, reproduction laser powerinformation, manufacturer's information, production number, lot numberor batch number, control number, copyright related information, key forciphering, key for deciphering, ciphered data, recording permissioncode, recording refusal code, reproducing permission code, andreproducing refusal code.

Further, an auxiliary information is such information that, for example,is described by the decimal number system or the hexadecimal notationand converted into the binary number system such as a BCD (Binary-CodedDecimal) code and a gray code.

Furthermore, the auxiliary information can accompany an error correctingcode in order to prevent a data error.

In addition, a reference clock is provided for representing a pause of acertain period of time on a signal. Actually, a reference clock iscomposed of a single frequency that will be mentioned later.

FIG. 5 is a plan view showing a structure of the microscopic pattern 20,which is embedded with an auxiliary information and a reference clock,of the information recording medium 1 according to the first embodimentof the present invention. That is, the microscopic pattern 20 iscomposed of a land portion “L” and a groove portion “G”.

Further, the land portion “L” or the groove portion “G” is formed bybeing wobbled. In other words, both an auxiliary information and areference clock are recorded by a wobbling groove. In FIG. 5, thedrawing is illustrated such that an auxiliary information and areference clock are recorded by wobbling a land portion “L”.

Furthermore, the microscopic pattern 20 is divided into at least twoareas macroscopically, and at least composed of an auxiliary informationarea 200 and a reference clock area 300. As mentioned above, each of theauxiliary information area 200 and the reference clock area 300 iswobbled respectively. By a wobbling groove, an auxiliary information isrecorded in the auxiliary information area 200 and a reference clock isrecorded in the reference clock area 300. These areas are continuouslyformed without being interrupted, so that continuous reproduction isenabled. FIG. 5 is illustrated such that only two areas of the auxiliaryinformation area 200 and the reference clock area 300 are allocated.However, this alternative allocation of the auxiliary information area200 and the reference clock area 300 is repeated and constitutes wholearea of the microscopic pattern 20 of the information recording medium1.

Moreover, in FIG. 5, both of the auxiliary information area 200 and thereference clock area 300 are formed on the land portion “L” as a mostpreferable example. How ever, it is essential that one of the auxiliaryinformation area 200 and the reference clock area 300 is formed on agroove portion “G” if the other one of the auxiliary information area200 and the reference clock area 300 is formed on a groove portion “G”.

As mentioned above, by forming the auxiliary information area 200 andthe reference clock area 300 on the same shaped portion, that is, a landportion “L” or a groove portion “G”, an auxiliary information and areference clock can be reproduced continuously.

The auxiliary information 200 is composed of a waveform that ismodulated digital data hereupon. Actually, the waveform is composed ofany one of an amplitude-shift keying modulation wave 250 (250, 251, and252), a frequency-shift keying modulation wave 260 (260, 261, and 262)and a phase-shift keying modulation wave 270 (270, 271, and 272) or anyone of them that are transformed. FIG. 5 exemplifies particularly thatthe auxiliary information 200 is the frequency-shift keying modulationwaveform 260 (260, 261, and 262).

Although these modulation methods will be detailed later, in theamplitude-shift keying modulation method, digital data of an auxiliaryinformation are expressed such as “1” or “0” by a fundamental wavewhether or not the fundamental wave is existed. In the case of thefrequency-shift keying modulation method, digital data of an auxiliaryinformation are expressed such as “1” or “0” by a frequency of afundamental wave whether the frequency is higher or lower. In the caseof the phase-shift keying modulation method, digital data of anauxiliary information are expressed such as “1” or “0” by a differenceof phase angular of a fundamental wave. It is possible to record anauxiliary information such as an address more efficiently and toallocate the reference clock area 200 relatively longer by adoptingthese modulation methods. Being able to allocate the reference clockarea 200 longer enables to detect a reference clock for a long period oftime when recording the information recording medium 1, so that stablerecording can be conducted.

A fundamental wave of these modulation methods hereupon can be selectedout from a sinusoidal wave (or cosine wave), a triangular wave, and arectangular wave. In case that a sinusoidal wave (cosine wave) isselected out from them, a harmonic component can be minimized whenreproducing, and resulted in improving power efficiency and suppressinga jitter. Consequently, a sinusoidal wave (cosine wave) is suitable fora fundamental wave.

In addition thereto, a signal waveform formed by any of these modulationmethods is recorded geometrically as a wobbling sidewall of land portion“L”.

On the other hand, the reference clock area 300 is composed of asingle-frequency wave 350 that is continuously repeated. Since thefrequency is single, it is possible to generate a frequency in responseto a number of revolutions by making the information recording medium 1move relatively while reproducing. Consequently, a reference clock canbe produced. The reference clock can be used for revolution control whenrecording.

Further, a fundamental wave having a single frequency is composed of anyone of a sinusoidal wave (cosine wave), a triangular wave, and arectangular wave. In case that a sinusoidal wave (cosine wave) isselected out from them, a harmonic component can be minimized whenreproducing, and resulted in improving power efficiency and suppressinga jitter. Consequently, a sinusoidal wave (cosine wave) is suitable fora fundamental wave.

In addition thereto, a signal waveform formed by any of these modulationmethods is recorded geometrically as a wobbling sidewall of land portion“L”.

As mentioned above, the microscopic pattern 20 according to the presentinvention is at least composed of the auxiliary information area 200 andthe reference clock area 300. An auxiliary information and a referenceclock are recorded continuously by a wobbling groove withoutinterruption. These auxiliary information and reference clock recordedon a sidewall of the land portion “L” in a shape of wobbling are readout from a push-pull signal by using a well-known 2-division or4-division detector. Revolution control can be conducted by the read-outreference clock while recording, and further an information can bewritten in or erased from a predetermined address by extracting anaddress information from an auxiliary signal.

It is desirable for reproduction that the auxiliary information area 200and the reference clock area 300 are in uniform length with each otherand allocated alternately. In case that a length is not uniform witheach other, it is not predicted that an auxiliary information such as anaddress or a reference clock can be detected at which timing whilereproducing. Consequently, confusions may occur. On the contrary, incase that each length is uniform and they are allocated alternately,arrival of a succeeding signal can be easily predicted once reproductionis enabled. Accordingly, a timing of obtaining an auxiliary informationand a reference clock is predicted by a logic circuit and the auxiliaryinformation and the reference clock can be reproduced in less error.

Further, the reference clock area 300 is an important signal forcontrolling a number of revolutions when reproducing the informationrecording medium 1, so that the reference clock area 300 is desirable tobe formed as long as possible. Actually, it is necessary for a ratio ofa length of the reference clock area 300 to a total length of theauxiliary information area 200 and the reference clock area 300 to bemore than 50%, desirably more than 60%. If the ratio is less than thevalue mentioned above, a reference clock can only be obtained for ashort period of time. Consequently, revolution control is conductedintermittently and a reproduction operation becomes unstable. In a worstcase, mismatching occurs in a logic circuit for reproducing and theoperation is resulted in interrupting the reproduction.

It is acceptable that a shape of fundamental waveform and an amount ofamplitude of these two areas are different from each other. However,they are desirable to be the same in view of simplification andstabilization of a recording circuit and a reproducing circuit.

With respect to a frequency, in case that the auxiliary information area200 is formed with the amplitude-shift keying modulation wave 250 or thephase-shift keying modulation wave 270, it is acceptable that afrequency of the amplitude-shift keying modulation wave 250 or thephase-shift keying modulation wave 270 is different from a frequency ofthe single-frequency wave 350 of the reference clock area 300. However,in case of the same frequency, the recording circuit and the reproducingcircuit can be simplified drastically. Consequently, the same frequencyis desirable. Their frequencies are desirable to be at least related to“integral multiples” or “one over an integer”.

Further, in case that an auxiliary information of the auxiliaryinformation area 200 is formed by the frequency-shift keying modulationwave 260, it is acceptable that two frequencies constituting thefrequency-shift keying modulation wave 260 are different from afrequency of the single-frequency wave 350 in the reference clock area300. However, in case that one of the two frequencies constituting thefrequency-shift keying modulation wave 260 is the same as the frequencyof the single-frequency wave 350, a physical length utilized forextracting a clock can be extended slightly. Consequently, the samefrequency is desirable. These three frequencies are desirable to berelated to “integral multiples” or “one over an integer” respectively inview of simplifying a recording circuit and a reproducing circuit.

Furthermore, it is also acceptable that a start-bit signal, a stop-bitsignal and a sync signal is recorded as a wobbling groove at theboundary between the auxiliary information area 200 and the referenceclock area 300 in order to clarify the division of them. With respect tosuch a signal, a single-frequency wave having a predetermined period anda predetermined frequency can be used. However, the predeterminedfrequency is essential to be at least different from the frequency ofthe single-frequency wave 350 that constitutes the reference clock area300. It is most desirable that the predetermined frequency is differentfrom any frequency constituting the single-frequency wave 350, theamplitude-shift keying modulation wave 250, the frequency-shift keyingmodulation wave 260, or the phase-shift keying modulation wave 270.

As mentioned above, the information recording medium 1 according to thefirst embodiment of the present invention can be in any shape such asdisciform, card and tape. Consequently, the microscopic pattern 20 thatis composed of approximately parallel grooves can also be in any shapesuch as spiral, coaxial and line. In case that the information recordingmedium 1 is in disciform and the microscopic pattern 20 is recordedspirally, the land portion “L” and the groove portion “G” is recorded bya recording method such as the constant angular velocity (CAV), theconstant linear velocity (CLV), the zone constant angular velocity(ZCAV) and the zone constant linear velocity (ZCLV) recording methods,wherein the ZCAV and the ZCLV recording methods are a method that formszones, which vary by radius, and conducts a different controlling systemindependent of each zone. In case that the information recording medium1 is recorded by the CLV recording method, for example, a same linearvelocity is maintained in the whole area of the information recordingmedium 1.

Further, in case of recording by the ZCAV recording method, the CLVrecording method is conducted in one zone and a controlling systemsimilar to the CAV recording method is conducted in the informationrecording medium 1 totally.

Furthermore, in case of recording by the ZCLV recording method, the CAVrecording method is conducted in one zone and a controlling systemsimilar to the CAV recording method is conducted in the informationrecording medium 1 totally.

FIG. 6 is an enlarged plan view of the reference clock area 300 in theinformation recording medium 1 on the basis of recording on a landportion “L” through the CLV recording method. In case that recording isconducted on a portion corresponding to a land portion “L” of therecording layer 12, an auxiliary information or a reference clock isessential to be extracted from the land portion “L”. Consequently, asingle-frequency wave 350 to be a reference clock must be recorded onthe land portion “L”. In view of that recording light scan along acenterline not shown of the land portion “L”, both sidewalls of the landportion “L” are essential to be parallel to each other. In other words,three land portions “L1” through “L3” (hereinafter generically referredto as land portion “L”) and two groove portions “G1” and “G2”(hereinafter generically referred to as groove portion “G”) areillustrated in FIG. 6.

Further, in FIG. 6, a sidewall of the inner circumferential side of theland portion “L2” or “L3” is shown as “L2 i” or “L3 i” (hereinaftergenerically referred to as inner sidewall “Li”) and another sidewall ofthe outer circumferential side of the land portion “L1” or “L2” is shownas “L1 o” or “L2 o” (hereinafter generically referred to as outersidewall “Lo”).

Further, a side wall of the outer circumferential side of the grooveportion “G1” or “G2” is shown as “G1 i” or “G2 i” (hereinaftergenerically referred to as inner sidewall “G1”) and another sidewall ofthe outer circumferential side of the groove portion “G1” and “G2” isshown as “G1 o” or “G2 o” (hereinafter generically referred to as outersidewall “Go”). The inner sidewall “Li” of the land portion “L” and theouter sidewall “Go” of the groove portion “G” represents the same wall,and the outer sidewall “Lo” of the land portion “L” and the innersidewall “G1” of the groove portion “G” represents the same wallhereupon.

Furthermore, a reference clock is recorded on the land portion “L” as asinusoidal-wave signal through the CLV recording method. Therefore, asshown in FIG. 6, three land portions “L1” through “L3” are not parallelto each other in almost all cases. However, in order to extract asinusoidal-wave signal accurately with avoiding interference from bothsidewalls caused by a phase shift of each sidewall, the inner sidewall“Li” and the outer sidewall “Lo” of the land portion “L” are essentialto be always formed in parallel to each other. From a point of viewcontrary to this, it is represented such that the inner sidewall “Gi”and the outer sidewall “Go” constituting the groove portion “G”, whichis the other portion than the land portion “L”, are never in parallel toeach other.

FIG. 7 is an enlarged plan view of the reference clock area 300 in theinformation recording medium 1 on the basis of recording on a landportion “ ” through the CAV recording method. In case that theinformation recording medium 1 is recorded by the CAV recording method,a same angular velocity is maintained in a whole area of the informationrecording medium 1. By this CAV recording method, the wobbling landportion “L” and the groove portion “G” can always be in parallel to eachother completely, so that a crosstalk amount between adjoining groovesbecomes constant at all times. Consequently, ideal reproduction that cansuppress output fluctuation of wobbling frequency and fluctuation in atime axis direction can be conducted. In other words, as shown in FIG.7, each land portion “L” becomes in parallel to each other and at thesame time each groove portion “G” also becomes in parallel to each otherdue to the characteristic of angular velocity. Three land portions “L1”through “L3” (hereinafter generically referred to as land portion “L”)and two groove portions “G1” and “G2” (hereinafter generically referredto as groove portion “G”) are illustrated in FIG. 7. In FIG. 7, asidewall of the inner circumferential side of the land portion “L2” or“L3” is shown as “L2 i” or “L3 i” (hereinafter generically referred toas inner sidewall “Li”) and another sidewall of the outercircumferential side of the land portion “L1” or “L2” is shown as “L1 o”or “L2 o” (hereinafter generically referred to as outer sidewall “Lo”).

Further, a side wall of the outer circumferential side of the grooveportion “G1” or “G2” is shown as “G1 i” or “G2 i” (hereinaftergenerically referred to as inner sidewall “G1”) and another sidewall ofthe outer circumferential side of the groove portion “G1” or “G2” isshown as “G1 o” or “G2 o” (hereinafter generically referred to as outersidewall “Go”). The inner sidewall “Ai” of the land portion “L” and theouter sidewall “Go” of the groove portion “G” represents the same wall,and the outer sidewall “Lo” of the land portion “L” and the innersidewall “Gi” of the groove portion “B” represents the same wallhereupon.

As mentioned above, in case of recording on a land portion “L” of therecording layer 12, for example, a clock is essential to be extractedfrom the land portion “L”. Therefore, the single-frequency wave 350 tobe a reference clock is recorded on the land portion “L”. The clock isrecorded by the CAV recording method, so that the three land portions“L1” through “L3” are completely in parallel to each other as shown inFIG. 7. At the same time, the groove portion “G” that is the restportion other than the land portion “L” is also in parallel to eachother perfectly. In other words, in order to extract a sinusoidal-wavesignal accurately, the inner sidewall “Li” and the outer sidewall “Lo”of the land portion “L” are essential to be always formed in parallel toeach other. However, in the case of recording by the CAV recordingmethod, the inner sidewall “Gi” and the outer sidewall “Go” of thegroove portion “G” is also formed to be in parallel to each other.

In either recording method of the CLV and the CAV, both the sidewallsconstituting the land portion “L”, that is, the inner sidewall “Li” andthe outer sidewall “Lo” of the land portion “L” are essential to be inparallel to each other.

Further, particularly in the case of recording by the CAV recordingmethod, not only the land portion “L” but also both the sidewalls “Gi”and “Go” constituting the groove portion “G” are in parallel to eachother. In other words, the inner sidewall “Li” and the outer sidewall“Lo” of the land portion “L” and the inner sidewall “Gi” and the outersidewall “Go” of the groove portion “G” are all in parallel to eachother.

The shape of the sidewall of the reference clock area 300 in themicroscopic pattern 20 recorded spirally in the information recordingmedium 1 in disciform is mentioned above. This situation is exactly thesame as for the auxiliary information area 200 due to a similar reasonfor the reference clock area 300. In other words, in either recordingmethod of the CLV and the CAV, both the sidewalls constituting the landportion “L”, that is, both the inner sidewall “Li” and the outersidewall “Lo” of the land portion “L” are essential to be in parallel toeach other.

In the information recording medium 1 according to the presentinvention, the auxiliary information area 200 and the reference clockarea 300 is continuously formed without interruption, so that bothsidewalls constituting the land portion “L”, that is, the inner sidewall“Li” and the outer sidewall “Lo” of the land portion “L” are formed inparallel to each other in any area on the information recording medium1.

With referring to FIG. 8, a wobbling amount Δ of a wobbling groove thatis formed in the information recording medium 1 according to the firstembodiment of the present invention is explained next.

FIG. 8 is an enlarged plan view of the microscopic pattern 20 formed bythe CLV recording method in the information recording medium 1 accordingto the first embodiment of the present invention. The microscopicpattern 20 is composed of the auxiliary information area 200 and thereference clock area 300, which are formed with a fundamental wave basedon the sinusoidal wave or the cosine wave and continue withoutinterruption. In FIG. 8, a centerline of wobbling groove is shown by achain line. A distance between two chain lines, which are adjacent toeach other, is defined as a pitch “P”.

Further, the information recording medium 1 shown in FIG. 8 is assumedto be recorded on a land portion “L” and a spot of reproducing lightbeam or a recording light beam that focuses on the land portion “L” isshown by a circle in doted line. The spot diameter is exhibited by “S”,that is equal to “λ/NA”, as mentioned above.

Furthermore, the land portion “L” wobbles and its wobbling width Δ inpeak to peak value is shown by two doted lines.

Moreover, in case that the information recording medium 1 is indisciform, a wobbling direction corresponds to a radial direction of thedisc-shaped information recording medium 1.

A reproducing apparatus of the information recording medium 1 canextract a wobbling amplitude of the auxiliary information area 200 andthe reference clock area 300 as a signal through a reproducing lightspot without interruption. In other words, by producing a push-pullsignal from reflected light of the reproducing light spot, asingle-frequency wave 350, a amplitude-shift keying modulation wave 250,a frequency-shift keying modulation wave 260, or a phase-shift keyingmodulation wave 270, which is based on a sinusoidal wave, can bedirectly extracted as a signal of similar figure. More accurately, atrack direction of wobbling groove is transformed into a time axisdirection, and further a radial direction of the wobbling groove istransformed into an amplitude direction of a reproduced signal, and thenthe single-frequency wave 350, the amplitude-shift keying modulationwave 250, the frequency-shift keying modulation wave 260, or thephase-shift keying modulation wave 270 is reproduced as the signal ofsimilar figure.

According to another aspect of the present invention, the informationrecording medium 1 of the first embodiment is formed with a wobblinggroove of which wobbling width Δ is within a range of Δ<P. In case thatthe information recording medium 1 is manufactured as mentioned above,adjacent tracks, that is, adjacent land portions “L”, for example, donot contact with each other physically, so that crosstalk caused byrecording can be avoided.

Further, the inventors of the present invention make an experiment on acase that a phase change material is used for the recording layer 12 andrecording is conducted by difference of reflectivity, phase difference,or both of them. In other words, the inventors try to reproduce anauxiliary information through a push-pull signal detecting method fromthe information recording medium 1 that is recorded with random data byconducting a phase change recording method. As a result of theexperiment, a limit of enabling to detect an auxiliary information is0.01S≦Δ. In case of a groove of which wobbling width Δ is formed to beless than 0.01S, random data caused by the phase change recording methodare superimposed extremely on an auxiliary information as a noise and anerror rate of the auxiliary information drastically increases.

On the contrary, the wobbling width Δ is set to the limitation of0.01S≦Δ, an auxiliary information can be reproduced sufficiently even ina low reflectivity condition such as an amorphous state due to the phasechange recording method. However, in case of 0.15S<Δ, a jitter in timeaxis direction occurs in an auxiliary information signal and a referenceclock signal due to an affection of reproduction crosstalk caused by anadjacent groove, particularly, stability of the reference clock signalis deteriorated.

Accordingly, a relation between the wobbling width Δ and the pitch Pshall be Δ<P, particularly, conditions satisfying relations Δ<P and0.01S≦Δ≦0.15S are most suitable for forming a wobbling groove.

FIG. 9 is an enlarged plan view of the microscopic pattern 20 of theinformation recording medium 1, wherein recording is conducted on therecording layer 12 of the information recording medium 1 shown in FIG.8. In FIG. 9, a record mark M is recorded on the land portions “L” thatare wobbled. The record mark M represents whether a modulated signal isON or OFF. There provided various lengths of record mark M as it will beexplained later. As mentioned above, the record mark M is formed on therecording layer 12. In case that the recording layer 12 is formed by aphase change material, a record mark M is recorded by reflectivity andphase difference, difference of reflectivity, or phase difference.

A structure of how a shape of wobbling groove is reflected to adifferential signal is complemented hereupon.

FIG. 10 is an enlarged plan view of a photo-detector 9 that collectsreproducing light, which is irradiated on the information recordingmedium 1 and reflected. In case that the photo-detector 9 is a4-division detector, as shown in FIG. 10, the detector 9 is divided intofour elements in accordance with the radial direction and the tangentialdirection of the information recording medium 1. A push-pull signal canbe produced by subtracting each sum signal in the tangential direction.More accurately, with defining that the four elements are A, B, C, and Drespectively, and further defining that electric currents, which areobtained from each of the elements A, B, C, and D when they receivelight, are Ia, Ib, Ic and Id respectively, the push-pull signal can berepresented by an equation “(Ia+Ib)−(Ic+Id)”. In other words, a signalto be obtained is a differential signal in the radial direction. When areproducing apparatus of the information recording medium 1 traces acenter of groove, that is, the center of the chain line shown in FIGS. 8and 9, the push-pull signal is in a form of obtaining an outputdifference in the radial direction with respect to the centerline.Consequently, a wobbling shape can be reproduced as a signal thatreflects the wobbling shape.

The total constitution of the information recording medium 1 accordingto the first embodiment of the present invention is detailed above.

Further, it is acceptable that the auxiliary information area 200 isconducted with not only recording on a sidewall by selecting onemodulation wave out of the amplitude-shift keying modulation wave 250,the frequency-shift keying modulation wave 260, and the phase-shiftkeying modulation wave 270 but also time-division recording on eachsidewall in different areas by selecting two or three modulationmethods.

A single-frequency wave can be superimposed on the amplitude-shiftkeying modulation wave 250, the frequency-shift keying modulation wave260, or the phase-shift keying modulation wave 270. In other words, withrespect to the amplitude-shift keying modulation wave 250 and thefrequency-shift keying modulation wave 260, a wave having a samefrequency as a frequency that constitutes those modulation waves or adifferent frequency from frequencies of those modulation waves can besuperimposed and recorded.

Particularly, with respect to the frequency-shift keying modulation wave260, a wave having either a higher frequency or a lower frequency of thefrequency-shift keying modulation wave 260 can be superimposed on thefrequency-shift keying modulation wave 260. Similarly, a wave having afrequency of “an integer multiple” or “one over an integer” of either ahigher frequency or a lower frequency of the frequency-shift keyingmodulation wave 260 can be superimposed on the frequency-shift keyingmodulation wave 260.

Further, with respect to the phase-shift keying modulation wave 270, awave having a frequency of “an integer multiple” or “one over aninteger” of the frequency constituting the phase-shift keying modulationwave 270 can be superimposed on the phase-shift keying modulation wave270.

In any case, by using a well-known band pass filter or phase detector,it is possible to separate a single-frequency wave and any of theamplitude-shift keying modulation wave 250, the frequency-shift keyingmodulation wave 260, and the phase-shift keying modulation wave 270 fromthe superimposed wave. For example, an experience is conducted withrespect to the phase-shift keying modulation wave 270. It is confirmedthat a single-frequency wave and a phase-shift keying modulation wavecan be separated as far as an amplitude ratio of the phase-shift keyingmodulation wave to the single-frequency wave is within a predeterminedrange of 1:5 to 5:1 while superimposing the single-frequency wave on thephase-shift keying modulation wave. In other words, in case that aninformation recording medium is manufactured as a trial by setting theamplitude ratio for out of the predetermined range, one wave havinglarger amplitude can be reproduced. However, the other wave havingsmaller amplitude can not be reproduced due to an excessively low signalto noise ratio (S/N).

In case of such a constitution that a single-frequency wave to besuperimposed and the single-frequency wave 350 of the reference clockarea 300 is the same frequency, a reference clock can also be extractedform the auxiliary information area 200. Consequently, such aconstitution is more suitable for recording by superimposing. That is tosay, since a reference clock continues substantially although theauxiliary information area 200 is formed over a long distance, extremelystable recording can be conducted.

It is acceptable that an auxiliary information to be formed on asidewall of a land portion “L” is highly discomposed and recorded withdistributed. By combining with dummy data “101”, for example,distributed recording is one recording method such that an auxiliaryinformation is recorded as a data array such as “101X”, wherein X iseither “0” or “1”, and the data array is allocated in each predeterminedinterval.

FIG. 11 is a first example showing a distributed recording of anauxiliary information. As shown in FIG. 11, the dummy data “101” as adata trigger “Tr” is allocated in the predetermined interval, at every11 bits herein, and an “X” is allocated in succession to the datatrigger “Tr”. In other words, by extracting only the “X” allocatedimmediately after the data trigger “Tr”, an auxiliary information can berestored. In this case, with defining that the “1” is data, theauxiliary information shown in FIG. 11 can be restored as a series ofdata that are composed of existing data (Data), none data (None) andexisting data (Data) in sequence, so that “101” can be reproduced as theauxiliary information. This recording method is effective for a formatthat is allowed to read a data array to be processed with spending alonger period of time. It is defined hereupon that one-bit data to beextracted at each predetermined interval is a “word” and an auxiliaryinformation is constituted by integrating a plurality of “words”.

Further, a variation of the recording method shown in FIG. 11 isexhibited in FIG. 12.

FIG. 12 is a second example showing a distributed recording of anauxiliary information. As shown in FIG. 12, a data trigger “Tr” and data“X” can be allocated with separating them in a predetermined bit ofinterval. In FIG. 12, the data trigger “Tr” is “11” and allocated atevery 11 bits. Data are recorded by “101” whether the “101” is existedor not in a predetermined interval. In other words, by extracting dataexisting in the fourth bit to the sixth bit, one-bit data can berestored. In this second example, data can be restored as a series ofdata composed of existing data (Data), none data (None) and existingdata (Data) in sequence, so that “101” is reproduced as the auxiliaryinformation. This recording method is effective for reducing erraticreadout because the data “X” is separated from the data trigger “Tr”.

Furthermore, with respect to a third example of the highly distributedrecording method, a first specific data pattern such as “11” isallocated or recorded at every predetermined interval. Then, a secondspecific data pattern such as “101” is allocated between the firstspecific patterns. A position at where the second specific pattern isallocated is advanced by a predetermined bit, distance or period withrespect to the first specific data pattern. Particularly, two positionsare allocated previously.

FIG. 13 is a third example of the highly distributed recording methodshowing a distributed recording of an auxiliary information. As shown inFIG. 13, a data trigger “Tr” or “11”, is allocated at everypredetermined interval, actually every 11 bits hereupon, as the firstspecific data pattern, and a second specific data pattern “101” isallocated between the data triggers “Tr” or “11”. A position at wherethe second specific data pattern is allocated is provided with twopositions; one is within a range of the third bit to the fifth bit fromthe data trigger “Tr” or “11” and the other is within a range of thefifth bit to the seventh bit. Decoding is conducted by judging that thesecond specific data pattern is allocated in either position. In thecase of FIG. 13, the second specific data pattern “101” is sequentiallyallocated in the positions starting with the third bit, fifth bit andthird bit respectively, so that data or words “101” can be reproduced asan auxiliary information. This recording method is effective forensuring higher reliability to an auxiliary information because therecording method can add a parameter whether or not the data “101” canbe read out to one of standards for judging reliability.

In other words, data to be recorded in an auxiliary information area areat least composed of a data trigger that is allocated at everypredetermined interval and data allocated at a predetermined positionbetween the data triggers. The information recording medium 1 accordingto the present invention is recorded with an auxiliary information by arelative distance between the data trigger and the data or the secondspecific data pattern.

In the description of the third example of the highly distributedrecording method mentioned above, the method of distributed recordingthat is conducted by using a position difference between the firstspecific data pattern and the second specific data pattern is explained.However, in case that a pattern, which is extremely high in readoutaccuracy, can be provided, it is acceptable for both the first specificdata pattern and the second specific data pattern that their patternsare the same pattern. In other words, decoding can be conducted byextracting a specific pattern having a shorter time interval from aspecific data pattern recorded at a predetermined time interval and bymeasuring a distance interval or the time interval between the specificdata pattern and the specific pattern. With referring to FIG. 14,further details are explained next.

FIG. 14 is a fourth example showing a distributed recording of anauxiliary information. As shown in FIG. 14, a data trigger “Tr” or “11”is allocated at a predetermined interval, at every 11 bits hereupon, asa first specific data pattern, and a second specific data pattern “11”having the same pattern as the data trigger “Tr” is allocated betweenthe data triggers “Tr”. A position at where the second specific datapattern is allocated is provided with two positions; one is within arange of the third bit to the fifth bit from the data trigger “Tr” or“11” and the other is within a range of the fifth bit to the seventhbit. Decoding is conducted by judging that the second specific datapattern is allocated in either position. In the case of FIG. 14, thesecond specific data pattern “11” is sequentially allocated in thepositions starting with the third bit, fifth bit and third bitrespectively, so that data or words “101” can be reproduced as anauxiliary information. This recording method is advantageous to areproducing circuit to be simplified because the recording methodrequires only one specific data pattern.

The highly distributed recording method is explained above in fourtypes. According to these highly distributed recording methods, anauxiliary information is recorded as data that are decomposed into everyone bit. Actually, some bits of dummy data are prepared for a datatrigger “Tr” first, and a data array composed of continuing single datasuch as continuing zeros, for example, is prepared next. The datatrigger “Tr” is connected with the single data array so as to beallocated at every predetermined interval for the data trigger “Tr”.Then, the auxiliary information that is decomposed into every one bit isrecorded so as to convert a part of the single data array by apredetermined rule. In other words, an auxiliary information is recordedby converting data allocated in a bit, which is advanced by apredetermined distance from the data trigger “Tr”, by the predeterminedrule.

On the other hand, when reproducing the auxiliary information, all dataare once read out from a sidewall of land portion “L” as a data arrayand a data trigger “Tr” that is allocated at every predeterminedinterval is detected from the data array. Then, one bit of data that isequivalent to a “Word” shown in FIGS. 11 to 14 is extracted from thedata array excluding the data trigger “Tr” with referring to thepredetermined rule. The auxiliary information is restored by integratingthe detected one-bit data.

The methods for recording in highly distributed and for reproducing aninformation recording medium according to the present invention areexplained above. In case of an auxiliary information, particularly, anaddress information, a plurality of zeros or ones may continue, so thatthere is existed a possibility of generating a DC component in a dataarray being read out. In order to eliminate such a possibility, it isacceptable that the data array is previously modulated by the base-bandmodulation method and recorded. In other words, there existed a methodsuch that a data array to be recorded on a sidewall of land portion “L”by wobbling modulation is previously replaced with another codes so asto reduce a sequence of zeros and ones to a certain number or less. Withrespect to such a method, the method such as Manchester code, PE (phaseencoding) modulation, MFM (modified frequency modulation), M2 (Millersquared) modulation, NRZI (non return to zero inverted) modulation, NRZ(non return to zero) modulation, RZ (return to zero) modulation anddifferential modulation can be used independently or by combining someof them together.

FIG. 15 is a table exhibiting data change before and after modulating abase-band.

With respect to a base-band modulation method, which is most suitablefor the information recording medium 1 of the present invention, thereis provided the Manchester code (biphase modulation) method. TheManchester code method is a method of applying two bits to each one bitof an original data to be recorded as shown in FIG. 15. That is, “00” or“11” is assigned to a data “0” to be recorded, and “01” or “10” to adata “1”.

Further, an inverted code of inverting a last code of preceding data isessentially applied to a head code of succeeding data when arranging thesucceeding data after the preceding data.

FIG. 16 is a table exhibiting an example of actual data change beforeand after modulating a base-band. As shown in FIG. 16, an original data“100001” is assigned to be a code array of “010011001101”. The originaldata contains a sequence of four “0”s and is an asymmetrical data inwhich an appearing probability of “0” is twice that of “1”. If such anasymmetrical data is modulated by the Manchester code method, a sequenceof “0” or “1” is only two maximally and the original data is convertedinto a symmetrical data having equal appearing probability of “0” and“1”. As mentioned above, the base-band modulation, which restricts asequence of same bits within a certain quantity, is effective toincrease stability of reading out data. Consequently, the base-bandmodulation method is suitable for pre-treatment for a long array ofauxiliary information.

An amplitude-shift keying modulation wave 250 (250, 251 and 252), afrequency-shift keying modulation wave 260 (260, 261 and 262) and aphase-shift keying modulation wave 270 (270, 271 and 272), which areused for the information recording medium 1 according to the embodimentone of the present invention as a wobbling groove modulation wave, areexplained next.

With referring to FIGS. 17 through 19, the amplitude-shift keyingmodulation waves 250, 251 and 252 are depicted.

FIG. 17 shows a first example of an amplitude-shift keying modulationwaveform according to the present invention. FIG. 18 shows a secondexample of an amplitude-shift keying modulation waveform according tothe present invention. FIG. 19 shows a third example of anamplitude-shift keying modulation waveform according to the presentinvention.

As shown in FIG. 17, the amplitude-shift keying modulation wave 250according to the present invention is geometrically recorded bymodulating data through the amplitude-shift keying modulation method andactually, constituted by an amplitude section 2501 and a non-amplitudesection 2500, wherein the amplitude section 2501 is formed by wobbling agroove in a predetermined period. In other words, the amplitude section2501 is a wobbling part of groove and the non-amplitude section 2500 isa non-wobbling part of groove.

Further, the amplitude section 2501 and the non-amplitude section 2500is corresponding to “1” and “0” of a data bit respectively. Theamplitude section 2501 is composed of a plurality of waves that continuemore than one cycle hereupon. A number of waves is not limited to aspecific cycle. However, if it is too many, length of the non-amplitudesection 2500 consequently becomes longer and resulting in that afundamental wave, which produces a gate when reproducing, is hardlydetected. Therefore, two to one hundred cycles, preferably three tothirty cycles are suitable for the number of waves of the amplitudesection 2501. As mentioned above, digital data (in case of FIG. 17, itis “10110”) is recorded by whether or not amplitude is existed. Thepush-pull signal detecting method mentioned above can be used forreading out the recorded data.

Furthermore, it should be understood that the amplitude-shift keyingmodulation wave 250 according to the present invention does not limiteach length or each amplitude size of the amplitude section 2501 and thenon-amplitude section 2500 to specific figure. In the case of theamplitude-shift keying modulation wave 250 shown in FIG. 17, the lengthof the amplitude section 2501 is set to be longer than that of thenon-amplitude section 2500.

In FIG. 18, an amplitude-shift keying modulation wave 251 is constitutedby amplitude sections 2511 a through 2511 c and non-amplitude sections2511. Each amplitude of the amplitude sections 2511 a through 2511 c isunequal to each other. However, unequal amplitude is acceptable for theamplitude-shift keying modulation method.

Further, it is also acceptable that assigning each amplitude in multiplelevels intentionally realizes recording in multi-values more than threevalues.

Furthermore, in case of an amplitude-shift keying modulation wave 252shown in FIG. 19, each amplitude of amplitude sections 2521 is equal toeach other and each length of the amplitude sections 2521 is equal tothat of non-amplitude sections 2520. This configuration is alsoacceptable for the amplitude-shift keying modulation method.Particularly, in case that data are recorded in digital by the binaryvalue of “0” and “1”, an isotropic layout as shown in FIG. 19 isdesirable for the digital recording by the binary value. In other words,if each height of the amplitude sections 2521 is made equal to eachother and each length of the amplitude sections 2521 is made equal tothat of the non-amplitude sections 2520, judging “0” or “1” whenreproducing can be realized by sufficient threshold value of amplitude.

Moreover, data arranged in series can be read out by one threshold valueof time, so that a reproducing circuit can be simplified.

In addition thereto, even in case that jitter exists in reproduced data,there is existed a merit that influence of the jitter can be minimized.

Further, with assuming that a code to be recorded is ideallysymmetrical, total length of the amplitude sections 2521 is made equalto that of the non-amplitude sections 2520 and resulted in that no DCcomponent is existed in a reproduced signal. It is advantageous todigital recording that no DC component releases a burden on datadecoding and servo.

As mentioned above, by using any of the amplitude-shift keyingmodulation waves 250, 251 and 252, an auxiliary information is recordedin an information recording medium 1 according to the first embodimentof the present invention. Either “0” or “1” is recorded in response towhether a wobble is existed on a sidewall of groove or not, so thatability of judging “0” or “1” is excellent. In other words, a low errorrate can be obtained although an auxiliary information is in relativelylow C/N (carrier to noise ratio).

Further, although recording on the recording layer 12 is conducted by auser, influence of random noise caused by the recording can be reducedand a low error rate can be maintained.

With referring to FIGS. 20 through 22, frequency-shift keying modulationwaves 260 through 262 are explained next.

FIG. 20 shows a first example of a frequency-shift keying modulationwaveform according to the present invention. FIG. 21 shows a secondexample of a frequency-shift keying modulation waveform according to thepresent invention. FIG. 22 shows a third example of a frequency-shiftkeying modulation waveform according to the present invention.

A frequency-shift keying modulation wave is for recording datageometrically by the frequency-shift keying modulation method and iscomposed of a plurality of sections that are formed by wobbling groovesby different frequencies. Actually, in the case of binary data, thefrequency-shift keying modulation wave is geometrically recorded byusing a higher frequency section and a lower frequency section. In caseof multi-valued data such as “n” values, a frequency-shift keyingmodulation wave is geometrically recorded by the frequency-shift keyingmodulation method that uses “n” kinds of frequency sections. Hereinafterthe examples are explained with assuming that data to be recorded are inbinary. FIG. 20 is one example of recording data “10110” geometrically.In FIG. 20, the frequency-shift keying modulation wave 260 is composedof three higher frequency sections 2601 and two lower frequency sections2600. The higher frequency section 2601 and the lower frequency section2600 are equivalent to “1” and “0” of a data bit respectively and theyare recorded in digital by changing the frequency at each one channelbit. A number of waves that constitute each frequency section is notlimited to one specific number. Each frequency section is composed of awave that continues more than one cycle. However, in consideration ofthat data are not redundant too much in a reproducing apparatus so as todetect a frequency accurately and to obtain a certain degree of datatransfer rate, each frequency section, which is corresponding to eachdata bit mentioned above, is desirable to be constituted by a number ofwaves within a range of one cycle to one hundred cycles, preferably onecycle to thirty cycles.

Further, it is acceptable that each amplitude of the higher frequencysection 2601 and the lower frequency section 2600 is equal to eachother. However, an amplitude ratio is not limited to one specificfigure. Amplitude of the higher frequency section 2601 can be formedlarger than that of the lower frequency section 2600 in consideration ofa frequency response of reproducing apparatus.

Furthermore, the push-pull signal detecting method mentioned above canbe used for reading out the recorded data.

It should be understood that the information recording medium 1according to the first embodiment of the present invention does notplace a restraint on physical length or amplitude size of a channel bit,which is composed of the higher frequency section 2601 and the lowerfrequency section 2600. For example, in FIG. 20, the physical length oflower frequency section 2600 is designated to be longer than that of thehigher frequency section 2601.

As shown in FIG. 21, in case of a frequency-shift keying modulation wave261, it is acceptable that amplitude of a higher frequency section 2611and a lower frequency section 2610 are equal to each other and length ofthe higher frequency section 2611 is equal to that of the lowerfrequency section 2610. By equalizing each amplitude and length asmentioned above, judging “0” or “1” can be conducted by sufficientthreshold value of amplitude when reproducing.

Further, data arranged in series can be read out by one threshold valueof time, so that a reproducing circuit can be simplified.

Furthermore, in case that jitter exists in reproduced data, there isexisted a merit that influence of the jitter can be minimized.

Moreover, with assuming that a code to be recorded is ideallysymmetrical, total length of the higher frequency sections 2611 is equalto that of the lower frequency sections 2610 and resulted in that no DCcomponent is existed in a reproduced signal. It is advantageous todigital recording that no DC component releases a burden on datadecoding and servo.

In FIGS. 20 and 21, the higher frequency section 2601 or 2611 and thelower frequency section 2600 or 2610 is connected to each otherrespectively, wherein each waveform rises at a point where a channel bitchanges. However, phase jump happens in probability of 50% at the momentwhen a channel bit changes. Consequently, a high frequency component isgenerated and resulted in deterioration of power efficiency per eachfrequency.

In order to eliminate such phase jump, a frequency-shift keyingmodulation wave 262 is provided. In FIG. 22, the frequency-shift keyingmodulation wave 262 is composed of a higher frequency section 2621 r or2621 f (hereinafter referred generically to as higher frequency section2621) and a lower frequency section 2620. The higher frequency section2621 and the lower frequency section 2620 is arranged so as to maintainphase continuity at a point where each channel bit of thefrequency-shift keying modulation wave 262 changes over. Actually, astarting phase of the lower frequency section 2620 is selected so as tobe that a phase direction of the end of the higher frequency section2621 and a phase direction of the start of the lower frequency section2620 are the same direction.

Further, the reverse connection is the same as such that a startingphase of the higher frequency section 2621 is selected so as to be thata phase direction of the end of the lower frequency section 2620 and aphase direction of the start of the higher frequency section 2621 arethe same direction. If the starting phase is selected as mentionedabove, continuity of phase is maintained and power efficiency isimproved.

Furthermore, a reproduction envelope becomes constant, so that a dataerror rate of auxiliary information, which is recorded in theinformation recording medium 1, is improved. Such a method ofmaintaining continuity of phase at a point where a channel bit changescan be applied to the auxiliary information area 200 and the referenceclock area 300 shown in FIG. 5. A data error rate of auxiliaryinformation is further improved if waveforms of the auxiliaryinformation area 200 and the reference clock area 300 are arranged asmentioned above.

A frequency of the higher frequency section 2621 (2601, 2611 or 2621)and the lower frequency section 2620 (2600, 2610 or 2620) is arbitraryselected. However, in order to eliminate interference with a frequencyrange that is provided for recording data on the information recordingmedium 1 by a user, it is strictly required for the higher frequencysection 2621 not to be extremely high frequency in comparison with afrequency of the lower frequency section 2620.

On the other hand, in order to improve a reproduction error rate ofaddress data, a frequency difference between the higher frequencysection 2621 and the lower frequency section 2620 shall be kept incertain degree so as to maintain excellent separativeness. From theseviewpoints, a frequency ratio of the higher frequency section 2621 tothe lower frequency section 2620 is desirable to be within a range of1.05 to 5.0, particularly, desirable to be within a range of 1.09 to1.67. In other words, phase relation between two frequencies isdesirable to be within a range of 2π±(π/20.5) to 2π±(π/0.75),particularly, desirable to be within a range of 2π±(π/12) to 2π±(π/2),that is, 360±15 degrees to 360±90 degrees, wherein the reference phaseis defined as 2π.

With respect to a frequency ratio (ratio of higher frequency to lowerfrequency), if the frequency ratio shown in FIG. 22 is assigned to be1.5, there exists a phase relation between these higher and lowerfrequencies such that the higher frequency is shifted by −π/2.5 from areference phase of a single-frequency wave and the lower frequency isshifted by +π/2.5 from the reference phase of the single-frequency wave,wherein the phase relation becomes 2π±(π/2.5) when the reference phaseis defined as 2π. In other words, the phase relation is shifted to360±72 degrees. It is expressed that these two frequencies are integralmultiple (wherein it is three times and two times respectively) of thefrequency (in this case 0.5) of the single-frequency wave. Consequently,it is advantageous for a demodulation circuit to be simplified.

Further, generating a clock signal becomes easier by using a circuithaving a window of 0.5.

Furthermore, a synchronous detector circuit can conduct demodulation. Inthis case, an error rate can be reduced extremely.

As mentioned above, an auxiliary information is recorded in theinformation recording medium 1 of the present invention by thefrequency-shift keying modulation waves 260, 261 and 262. The binarydata “0” or “1” is recorded in accordance with change of a wobblingfrequency, so that ability of judging “0” or “1” is excellent. In otherwords, an auxiliary information can be obtained in a low error ratealthough a C/N is relatively low.

More, influence of random noise caused by recording on the recordinglayer 12 by a user can be reduced and a low error rate can bemaintained.

With referring to FIGS. 23 through 25, phase-shift keying modulationwaves 270, 271 and 272 are explained next.

FIG. 23 shows a first example of a phase-shift keying modulationwaveform according to the present invention. FIG. 24 shows a secondexample of a phase-shift keying modulation waveform according to thepresent invention. FIG. 25 shows a third example of a phase-shift keyingmodulation waveform according to the present invention.

As shown in FIG. 23, the phase-shift keying modulation wave 270 isformed by recording data geometrically by the phase-shift keyingmodulation method. Actually, the phase-shift keying modulation wave 270is composed of a plurality of sections, which are constituted bywobbling a groove by a predetermined frequency. In the case of binarydata, the phase-shift keying modulation wave 270 is composed of anadvancing phase section 2701 and a receding phase section 2700. In caseof multi-valued data such as “n” values, a phase-shift keying modulationwave is composed of “n” phase sections, which correspond to “n” kinds ofphases respectively. Hereinafter the examples are explained withassuming that data to be recorded are in binary. FIG. 23 is one exampleof recording data “10110” geometrically. In FIG. 23, the phase-shiftkeying modulation wave 270 is composed of three advancing phase sections2701 and two receding phase sections 2700. The advancing phase section2701 and the receding phase section 2700 are equivalent to “1” and “0”of a data bit respectively, and recorded in digital by changing thephase at each one channel bit. Actually, the advancing phase section2701 and the receding phase section 2700 are exhibited by a sinusoidalwave of “sin 0” and another sinusoidal wave of “sin(−π)” respectively.As shown in FIG. 23, the advancing phase section 2701 and the recedingphase section 2700 are constituted by one cycle of waveformrespectively. However, phase difference between them is as many as π, sothat they can be separated and reproduced sufficiently by the envelopedetection method or the synchronous detection method.

Each frequency of the advancing phase section 2701 and the recedingphase section 2700 is identical to each other. A number of waves, whichconstitutes the advancing phase section 2701 and the receding phasesection 2700, is not restricted to a specific number. Both phasesections are composed of a wave that continues more than one cycle.However, in consideration of that data are not redundant too much in areproducing apparatus so as to detect a frequency accurately and toobtain a certain degree of data transfer rate, each phase sectioncorresponding to each data bit that is mentioned above is desirable tobe constituted by a number of waves within a range of one cycle to onehundred cycles, preferably one cycle to thirty cycles.

It is acceptable for each physical length of the advancing phase section2701 and the receding phase section 2700 to be identical or not. In casethat each physical length is identical, data, which are combined inseries, can be divided into piece by a predetermined time, that is, apredetermined clock when reproducing. Consequently, a reproductioncircuit can be simplified.

Further, in case that jitter exists in reproduced data, there is existeda merit that enables to minimize influence of the jitter.

It is also acceptable for each amplitude of the advancing phase section2701 and the receding phase section 2700 to be coincide with each otheror not. However, in consideration of easier reproduction, it isdesirable for the advancing phase section 2701 and the receding phasesection 2700 that each amplitude of them coincides with each other.

The information recording medium 1 according to the first embodiment ofthe present invention can deal with not only binary data but alsomulti-valued data. Dealing with how many kinds of phases depends on thatphase difference of each data bit can be separated into what degree ofresolution. The limit of separation of the information recording medium1 is obtained experimentally by the inventors of the present inventionand it is confirmed that phase difference can be separated into up toπ/8. In other words, various phase sections, which constitute themulti-valued channel bit, can deal with minimum phase difference of eachphase section within a range of π/8 to π, wherein π is equivalent tominimum phase difference of a binary data. That is to say, a wide rangeof data from binary to hexadecimal can be dealt with.

FIG. 24 is a second example showing a phase-shift keying modulation wave271 that is recorded with 4-valued data. In FIG. 24 the phase-shiftkeying modulation wave 271 is composed of a first phase [sin(−3π/4)]section 2710, a second phase [sin(−π/4)] section 2711, a third phase[sin(π/4)] section 2712 and a fourth phase [sin(3π/4)] section 2713.Minimum phase difference of each phase section is π/2, so that each ofthe 4-valued data can be sufficiently separated and obtained. Hereupon,the first phase section 2710, the second phase section 2711, the thirdphase section 2712 and the fourth phase section 2713 are corresponded todata “1”, “2”, “3” and “4” respectively for convenience.

When recording multi-valued data such as mentioned above, themulti-valued data can be replaced by multidimensional data. Withassuming that the data is two-dimensional data (x, y), for example, thedata “1” through “4” can be replaced by data (0, 0), data (0, 1), data(1, 0), and data (1, 1) respectively.

FIG. 25 is a third example showing a phase-shift keying modulation wave272, which deals with binary data in the information recording medium 1according to the first embodiment of the present invention. In FIG. 25,a fundamental wave is a saw-tooth wave and the waveform is asymmetricalfor rising and falling sections. By controlling the rising and fallingsections individually, difference of phase is exhibited. In the case ofthe waveform shown in FIG. 25, data “1” is recorded as a section 2721 ofwhich a wave rises gradually and falls rapidly (hereinafter referred toas a rapidly falling section 2721), and data “0” as a section 2720,which rises rapidly and falls gradually (hereinafter referred to as arapidly rising section 2720). In case that address data “10110” isrecorded, for example, as shown in FIG. 25, the phase-shift keyingmodulation wave 272 is geometrically recorded with the rapidly fallingsection 2721, the rapidly rising section 2720, the rapidly fallingsection 2721, the rapidly falling section 2721 and the rapidly risingsection 2720 in order. Such a recording method that records data byangle difference between a rising angle and a falling angle candemodulate the data by inputting the data into a high-pass filter and byextracting a differential component. Consequently, the recording methodis advantageous to the data that can be reproduced even under low C/Ncondition.

As mentioned above, an auxiliary information is recorded in theinformation recording medium 1 according to the first embodiment of thepresent invention by the phase-shift keying modulation wave 270, 271 or272. The binary data “0” or “1” is recorded in accordance with phasechange of a number of wobbles, so that ability of judging “0” or “1” isexcellent. Particularly, a frequency of the phase-shift keyingmodulation method is constant. Therefore, a filter, which is installedin a preceding stage of a demodulation circuit for auxiliaryinformation, can be assigned to be a band-pass filter of which passingband is specialized in one frequency.

Further, the band-pass filter can also eliminate any kind of noisesincluding a noise that is caused by recording by a user effectively. Inother words, a lower error rate can be obtained even though a C/N isrelatively low.

Furthermore, influence of random noise caused by the recording can beeffectively eliminated and a low error rate can be maintained, eventhough recording in the recording layer 12 of the information recordingmedium 1 is conducted by a user.

As mentioned above, constitutions and effects of the amplitude-shiftkeying modulation waves 250, 251 and 252, the frequency-shift keyingmodulation waves 260, 261 and 262 and the phase-shift keying modulationwaves 270, 271 and 272 according to the present invention are depicted.In the above-mentioned descriptions that are explained with referring toFIGS. 17 through 25, they are explained as examples with defining that afundamental wave is a sinusoidal wave and recorded. However, it is alsoacceptable that a fundamental wave is defined as a cosine wave andrecorded.

The constitution and the effect of the information recording medium 1according to the first embodiment of the present invention is detailedabove. However, the inventive concept of the present invention is notlimited to the information recording medium 1 that is described withreferring to FIGS. 1 though 25. It is apparent that many changes,modifications and variations in the arrangement of equipment and devicesand in materials can be made without departing from the inventionconcept disclosed herein.

Further, in the above-mentioned first embodiment, each constitutingcomponent can be replaced by each other or exchanged by anothercomponent that is disclosed herein.

For example, the shape of the information recording medium 1 is notrestricted to one specific shape, any shape such as disc, card and tapecan be applied for the information recording medium 1. It is alsoapplicable for the information recording medium 1 to be a shape incircular, rectangular or elliptic.

In addition, an information recording medium having a hole is alsoacceptable.

FIG. 26 shows a first example of disk-shaped information recordingmedium 1 having a hole. FIG. 27 shows a second example of card-shapedinformation recording medium 1A having no hole. FIG. 28 shows a thirdexample of a card-shaped information recording medium 1B having a hole.In FIG. 26, the disc-shaped information recording medium 1 is formedwith a microscopic pattern 20, which is constituted by a continuoussubstance of approximately parallel grooves in a circular arc and inparallel with the inner or outer circumference of the informationrecording medium 1. The form of the microscopic pattern 20 is notlimited to be the circular arc. Any form that is arranged continuouslyin 360 degrees coaxially or spirally is also acceptable. In FIG. 27, thecard-shaped information recording medium 1A having no hole is formedwith a microscopic pattern 20, which is constituted by a continuoussubstance of approximately parallel grooves linearly and in parallelwith the longitudinal direction of the information recording medium 1A.In FIG. 28, the card-shaped information recording medium 1B having ahole is formed with a microscopic pattern 20, which is constituted by acontinuous substance of approximately parallel grooves in circular.

Further, the cross section of the information recording medium 1explained by using FIG. 1 is not limited to the cross sectional viewshown in FIG. 1. It is apparent that the invention concept of thepresent invention can apply to an information recording medium havingvarious cross sectional configurations.

Second Embodiment

FIG. 29 is a cross sectional view of an information recording mediumaccording to a second embodiment of the present invention. In FIG. 29,an information recording medium 2 is identical to the informationrecording medium 1 shown in FIG. 1 except for the light transmittinglayer 11, so that details of the same components will be omitted. Asshown in FIG. 29, the light transmitting layer 11 of the informationrecording medium 1 is divided into two layers; a light transmittinglayer 11 a and an adhesive light transmitting layer 11 b, wherein thelight transmitting layer 11 a is similar to the light transmitting layer11 as mentioned above. The adhesive light transmitting layer 11 b is alayer for adhering the light transmitting layer 11 a on the recordinglayer 12 firmly, and transmits more than 70% of light having awavelength λ, desirably more than 80%.

With respect to a material of the adhesive light transmitting layer 11a, an adhesive or cohesive resin such as thermosetting resins, variousenergy ray curable resins including UV ray curable resins, visibleradiation curable resins and electron beam curable resins, moisturecurable resins, plural liquid mixture curable resins and thermoplasticresins containing solvent can be used.

Further, a thickness of the adhesive light transmitting layer 11 b ismore than 0.001 mm as a minimum thickness exhibiting adhesiveness,desirably less than 0.04 mm in view of preventing a growth of stresscrack, and more desirably to be more than 0.001 mm and less than 0.03mm. Desirably further more, the thickness is more than 0.001 and lessthan 0.02 mm. However, it is the most desirable that the thickness ismore than 0.001 mm and less than 0.01 mm in view of warpage of theinformation recording medium 2 totally.

Third Embodiment

FIG. 30 is a cross sectional view of an information recording mediumaccording to a third embodiment of the present invention. In FIG. 30, aninformation recording medium 3 is identical to the information recordingmedium 1 shown in FIG. 1 except for the substrate 13, so that details ofthe same components will be omitted. As shown in FIG. 30, the substrate13 shown in FIG. 1 is replace with a substance of two-layer structure; asubstrate 13 a and a resin layer 14.

With respect to a material of the resin layer 14, such resins asthermosetting resins, various energy ray curable resins including UV raycurable resins, visible radiation curable resins and electron beamcurable resins, moisture curable resins, plural liquid mixture curableresins and thermoplastic resins containing solvent can be used.Reproducing light never reaches to the resin layer 14, so that there isexisted no limitation in transmittance.

Further, a thickness of the resin layer 14 is desirable to be less than0.02 mm in view of warpage of the information recording medium 3totally.

Fourth Embodiment

FIG. 31 is a cross sectional view of an information recording mediumaccording to a fourth embodiment of the present invention. In FIG. 31,an information recording medium 4 is identical to the informationrecording medium 1 shown in FIG. 1 except for the light transmittinglayer 11 and the substrate 13, so that details of the same componentswill be omitted. As shown in FIG. 31, the light transmitting layer 11 ofthe information recording medium 1 is divided into two layers; a lighttransmitting layer 11 a and an adhesive light transmitting layer 11 b assame constitution as those of the information recording medium 2 shownin FIG. 29.

Further, the substrate 13 shown in FIG. 1 is replace with a substance oftwo-layer structure; a flat substrate 13 b and a pattern transferringlayer 15 having a microscopic pattern 22, wherein the patterntransferring layer 15 is an extremely thin film for having themicroscopic pattern 22.

Furthermore, a material of the pattern transferring layer 15 is selectedout from a metal, an alloy of the metal and a resin, wherein an alloyincludes a compound such as oxide, nitride, carbide, sulfide andfluoride, and its thickness is designated to be within a range of 5 nmto 200 nm.

With respect to a typical example of resin, there is existed novolaclight-sensitive resin and polyhydroxy styrene light-sensitive resin,wherein both resins can be developed by alkali.

Each component of the information recording mediums 1 through 4 shown inFIGS. 1 through 4 and 26 through 31 can be replaced by or combined withother component mutually as far as a reproduction characteristic is notdeteriorated.

For example, it is acceptable to stick two information recording mediumsout of the information recording mediums 1 through 4, wherein oneinformation recording medium is stuck on the other information recordingmedium with facing each substrate 13 (13 a, 13 b) towards each other.

Further, one set of the recording layer 12 and the light transmittinglayer 11 can be stuck on the light transmitting layer 11 of theinformation recording mediums 1 through 4. By this configuration,capacity of the information recording mediums 1 through 4 can beincreased almost twice.

Furthermore, it is acceptable that laminating a plurality of sets of therecording layer 12 and the light transmitting layer 11 repeatedly formsa multi-layered information recording medium having a plurality ofrecording layers.

Further, the information recording mediums 1 through 4 according to thefirst through fourth embodiment of the present invention can be formedwith commonly known layers such as an antistatic layer, a lubricativelayer and a hard coat layer that are laminated on the light transmittinglayer 11 (or 11 a) although they are not shown in drawings.

With respect to an actual material for the antistatic layer, a resinsuch as energy ray curable resin and thermosetting resin that aredispersed with surface-active agent and conductive fine particles can beused.

With respect to an actual material for the lubricative layer, liquidlubricant of which surface energy is adjusted by modifying hydrocarbonmacromolecule with silicon and fluorine can be used. A thickness of thelubricative layer is desirable to be within a range of 0.1 nm to 10 nmapproximately.

Further, with respect to an actual material for the hard coat layer, aresin, which transmits more than 70% of light having wavelength λ, suchas thermosetting resins, various energy ray curable resins including UVray curable resins, visible radiation curable resins and electron beamcurable resins, moisture curable resins, plural liquid mixture curableresins and thermoplastic resins containing solvent can be used.

Furthermore, the hard coat layer is desirable to exceed a certain valueof the “scratch test by pencil” regulated by the Japanese IndustrialStandard (JIS) K5400 in consideration of abrasion resistance of thelight transmitting layer 11 (or 11 a). In consideration of that glass isa hardest material for an objective lens of a reproducing apparatus ofinformation recording medium, a value of the “scratch test by pencil”for the hard coat layer is most preferable to be more than the “H”grade. If the test value is less than the “H” grade, dust that is causedby scraping the hard coat layer is remarkably generated and resulted indeteriorating an error rate abruptly.

Moreover, a thickness of the hard coat layer is desirable to be morethan 0.001 mm in consideration of shock resistance. However, thethickness is more desirable to be less than 0.01 mm in consideration ofeach warp of the information recording mediums 1 through 4 totally.

Further, a thin film, which transmits more than 70% of light having awavelength λ, and has a value of the “scratch test by pencil” of morethan the “H” grade, can be used for the hard coat layer. With respect toan actual example of the thin film, an element such as carbon,molybdenum and silicon, and their alloy including composition such asoxide, nitride, sulfide, fluoride and carbide can be used. A filmthickness of such a thin film is desirable to be within a range of 1 nmto 1000 nm.

Furthermore, a label printing can be applied on the outer surface of thesubstrate 13 (13 a, 13 b) opposite to the recording layer 12 althoughthe label printing is not shown in any drawings. Various energy raycurable resins containing pigment and dye such as UV ray curable resins,visible radiation curable resins and electron beam curable resins can beused suitably for the label printing. A thickness of the label printingis desirable to be more than 0.001 mm in consideration of visibility ofthe printing, more desirable to be less than 0.05 mm in consideration ofeach warp of the information recording mediums 1 through 4 totally.

A cross sectional surface of a groove portion “G” and a land portion “L”in the microscopic patterns 20, 21 and 22 is formed flat respectively.However, a cross sectional surface is not limited to flat.Cross-sectionally, they can be formed in a shape of a V-letter or aninverse V-letter.

Further, any of the information recording mediums 1, 2, 3 and 4 can beformed with a read-only area on the plane of the information recordingmedium other than a predetermined area for recording, that is, an areafor recording and reproducing. The read-only area can be formed by a pitor a wobbling groove recorded with at least one modulation wave selectedout from the amplitude-shift keying modulation wave 250, thefrequency-shift keying modulation wave 260 and the phase-shift keyingmodulation wave 270 on a sidewall of the groove. The informationrecording medium can be provided with the reference clock area 300together with the read-only area hereupon. These read-only area andreference clock area 300 can be formed by a bar code. The read-only areacan provide information for tuning a recording apparatus or areproducing apparatus when recording or reproducing.

Furthermore, the read-only area can handle an identificationinformation, a copyright information and a copy restriction informationof an individual information recording medium.

Moreover, the read-only area can be allocated arbitrarily. However, incase of an information recording medium in disciform, it is consideredthat a read-only area and a recording and reproducing area is allocatedin the inner circumference area and the outer circumference arearespectively, and these areas are formed so as not to overlap with eachother. Particularly, it is most desirable that these two areas come intocontact with each other, and they are connected at one point andresulted in enabling to be reproduced continuously.

A hologram and a visible microscopic pattern for identifying theinformation recording medium 1, 2, 3 or 4 can be formed in an area otherthan a predetermined area for recording.

In order to improve ability of loading an information recording mediuminto a reproducing apparatus or a recording apparatus, and in order toimprove protectiveness while loading and handling the informationrecording medium, each of the information recording mediums 1 through 4can be contained in a cartridge.

In case that the information recording mediums 1 through 4 are indisciform, its dimensions are not limited to one dimension. For example,in the case of diameter, various diameters from 20 mm to 400 mm can beapplied for the information recording mediums 1 through 4. Any diametersuch as 30, 32, 35, 41, 51, 60, 65, 80, 88, 120, 130, 200, 300 and 356mm can be acceptable.

The recording layer 12 provided in the information recording mediums 1through 4 are shown as a single layer in the respective drawings.However, the recording layers 12 can be formed by a plurality of thinfilm materials for a purpose of improving recording and reproducingcharacteristics and storage stability.

With referring to FIG. 32, another embodiment of information recordingmedium is detailed next.

Fifth Embodiment

FIG. 32 is a cross sectional view of an information recording mediumaccording to a fifth embodiment of the present invention. In FIG. 32, aninformation recording medium 5 is similar to the information recordingmedium 1 of the first embodiment shown in FIG. 1, so that the samecomposition or configuration as that of the information recording medium1 is marked by the same symbol as the information recording medium 1 andits detail is omitted. As shown in FIG. 32, the information recordingmedium 5 according to the fifth embodiment of the present invention iscomposed of a reflective layer 121, a first protective layer 122, arecording layer 123, a second protective layer 124, and a lighttransmitting layer 11, which are sequentially formed on a substrate 13having a microscopic pattern 20 in order.

With respect to a material for the reflective layer 121, there existed ametal having light reflectiveness such as Al, Au and Ag, an alloy thatcontains the metal as a main component and an additive element composedof more than one metal, semiconductor or semimetal, and a mixture ofmetal such as Al, Au and Ag with metal compound such as metal nitride,metal oxide and metal chalcogenide. Such a metal as Al, Au or Ag and analloy containing the metal as the main component is high in lightreflectiveness and thermal conductivity, so that they are preferable forthe material of the reflective layer 121.

Further, the reflective layer 121 plays a role of optimizing conductionof heat when recording is conducted to the recording layer 123, so thatthe reflective layer 121 can be called a heat-sink layer.

With respect to the alloy mentioned above, there existed an alloycomposed of Al or Ag added with at least one element out of Si, Mg, Cu,Pd, Ti, Cr, Hf, Ta, Nb, Mn, Pd, Zr and Rh as an additive element withina range of more than 1 atomic % to less than 5 atomic % in total orcomposed of Au added with at least one element out of Cr, Ag, Cu, Pd, Ptand Ni as an additive element within a range of more than 1 atomic % toless than 20 atomic % in total.

Particularly, as anti-corrosiveness is excellent and an iterativecharacteristic is improved, the reflective layer 121 is desirable to beconstituted by any one of Al—Cr alloy, Al—Ti alloy, Al—Ta alloy, Al—Zralloy, Al—Ti—Cr alloy and Al—Si—Mn alloy, which contain Al as a maincomponent and an additive element that is designated to be within arange of more than 0.5 atomic % to less than 3 atomic %. With respect tothe additive element, adding a metal or a semiconductor to a base metalalone makes a crystal particle smaller and results in reducing noiselevel while reproducing, so that adding additive element is desirable.

Furthermore, adding additive element is effective for improvingstability under a high temperature and high humidity condition. Alloyssuch as Al—Ti, Al—Cr, Al—Zr, Al—Si, Ag—Pd—Cu and Ag—Rh—Cu, for example,are desirable for the material of the reflective layer 121. In case ofutilizing a violaceous semiconductor laser, constituting the reflectivelayer 121 by an alloy of Al system or Ag system can obtain higherreflectivity. A thickness of the reflective layer 121 is within a rangeof 10 nm to 300 nm.

More, the thickness of the reflective layer 121 varies by a degree ofthermal conductivity of a metal or an alloy constituting the reflectivelayer 121. In case of Al—Cr alloy, for example, thermal conductivitydecreases in accordance with content of Cr that increases. Consequently,the thickness of the reflective layer 121 must be made thicker;otherwise increasing content of Cr does not comply with recordingstrategy. In case that content of Cr is larger, the reflective layer 121is hard to be heated or cooled down and becomes a so-called graduallycooling structure. In order to control forming a record mark inaccordance with the recording strategy, some consideration such thatshortening a head pulse, shortening multi-pulses or extending a coolingpulse is required. In case that the thickness of the reflective layer121 exceeds 50 nm, the reflective layer 121 does not change optically oraffect a value of reflectivity. However, affection to a cooling speedincreases extremely. In case of increasing the thickness of thereflective layer 121 to more than 300 nm, it takes extra time whilemanufacturing an information recording medium. Consequently, it isdesirable for the film thickness of the reflective layer 121 to besuppressed possibly by using a material having higher reflectivity.

Moreover, by dividing the reflective layer 121 into more than twolayers, a noise level while reproducing an information recording mediumcan be reduced. Such a reflective layer 121 composed of more than twolayers is formed as follows. In case of forming the reflective layer 121having a thickness of 150 nm in total by using a single disc sputteringsystem, which forms each layer on a substrate 13 in a plurality ofvacuum chambers while transporting the substrate 13 one by one, a firstreflective layer is formed by a first material in a first vacuum chamberat a filming speed of 2 nm/s, and then second and third reflectivelayers are formed in second and third vacuum chambers respectively at afilming speed of 6.5 nm/s. Consequently, a plurality of the substrates13 (discs) can be filmed one after another in a short period of time aslong as 10 seconds. By the above-mentioned process, a crystal particlecan be made finer by changing a filming speed.

Accordingly, a noise level can be reduced when reproducing theinformation recording medium 5.

The first protective layer 122 and the second protective layer 124 iseffective for protecting the substrate 13 and the recording layer 123from deformation and resulting in deteriorating a recordingcharacteristic by excessive heat while recording, for preventingoxidization of recording materials, and effective for improving a signalcontrast by an optical interference effect while reproducing.

Further, these first and second protective layers 122 and 124 aretransparent at a wavelength of a light beam for recording andreproducing and its refractive index “n” is within a range of 1.9≦n≦2.5.

Furthermore, both the first protective layer 122 and the secondprotective layer 124 are not required to be made by same material andcomposition. It is acceptable to be constituted by different materials.A thickness of the second protective layer 124 decides a wavelengthexhibiting a minimum value of spectral reflectance.

Moreover, the first protective layer 122 and the second protective layer124 is further effective for activating crystallization of a recordinglayer and for improving an erase ratio.

With respect to a material of these first and second protective layers122 and 124, there is provided an inorganic thin film such as ZnS, SiO₂,silicon nitride, and aluminum oxide.

Particularly, an oxidized thin film of metal or semiconductor such asSi, Ge, Al, Ti, Zr and Ta, a nitride thin film of metal or semiconductorsuch as Si, Ge and Al, a carbide thin film of metal or semiconductorsuch as Ti, Zr, Hf and Si, a sulfide thin film of metal or semiconductorsuch as ZnS, In₂S₃, TaS₄ and GeS₂ and a film of mixture compoundcontaining more than two compounds out of the above-mentioned compoundssuch as oxide, nitride, carbide and sulfide are desirable for the firstand second protective layers 122 and 124 because they are high in heatresistance and chemically stable.

Further, with respect to a material of the first and second protectivelayers 122 and 124, it is desirable that the material does not diffuseinto the recording layer 123. Compounds of oxide, sulfide, nitride andcarbide are not necessary to be a stoichiometrical composition.Controlling a composition and using them by mixing are also effectivefor controlling a refractive index. By changing a content amount ofoxygen, sulfur, nitrogen and carbon, a refractive index “n” iscontrolled. If a content amount of them increases, a refractive index“n” decreases. A mixture film of ZnS and SiO₂ is particularly desirablefor a material of the first and second protective layers 122 and 124,because recording sensitivity, C/N (carrier to noise ratio), and anerase ratio is hard to be deteriorated by a plurality of repetitions ofrecording and reproducing. A thickness of the first protective layer 122and the second protective layer 124 is within a range of 10 nm to 500 nmrespectively. Particularly, a thickness of the first protective layer122 is desirable to be within a range of 10 nm to 50 nm because ofexcellent recording characteristics such as C/N and erase ratio andenabling to rewrite stably a plurality of times. If a thickness of thesecond protective layer 122 is thinner, a reflectivity increases and arecording sensitivity results in being deteriorated.

Furthermore, the thinner first protective layer 122 makes a spacebetween the second protective layer 122 and the reflective layer 121narrower and the recording layer 123 results in a so-called rapidcooling construction, so that a relatively large recording power isnecessary for forming a record mark.

On the contrary, if the thickness of second protective layer 122 becomesthicker, the space between the protective layer 122 and the reflectivelayer 121 becomes wider and the recording layer 123 becomes thegradually cooling structure. Consequently, a rewriting performance isdeteriorated and a number of repetitions of overwriting decreases. Afilm thickness of the first protective layer 122 is preferable to bethinner than that of the second protective layer 124 and to beconstituted in the rapid cooling construction so as to relief thermaldamage. Consequently, the film thickness of the first protective layer122 is preferable to be within a range of 2 nm to 50 nm. Desirably, afilming speed of the first protective layer 122 is made slower than thatof the second protective layer 124.

Accordingly, an increase of jitter caused by rewriting is suppressed anda number of repetitions of overwriting increases.

With respect to a material of the recording layer 123, the same phasechange material as the recording layer 12 mentioned above is used. Afilm thickness of the recording layer 123 is within a range of 5 nm to100 nm, desirably, 10 nm to 30 nm in order to increase a reproducedsignal.

The same material as the first protective layer 122 is used for thesecond protective layer 124. A thickness of the second protective layer124 is within a range of 10 nm to 200 nm. Desirably, the thickness iswithin a range of 40 nm to 150 nm to increase a reproduced signalalthough an optimum film thickness varies by a wavelength of a lightsource to be utilized. In case that recording light is a violaceouslaser having a wavelength of 400 nm approximately, modulated amplitudecan be increased by adjusting the thickness to be within a range of 40nm to 60 nm.

According to the present invention, as mentioned above, the recordingcharacteristics and the reproducing characteristics of the informationrecording medium 5 is improved in addition to the effects realized bythe information recording medium 1. The laminated constitution of theinformation recording medium 5 can be applied for not only theinformation recording medium 1 but also the information recordingmediums 2 through 4.

Further, in order to improve the recording characteristics and thereproducing characteristics more, an auxiliary thin film can be formedon a surface of each layer or between layers.

The information recording mediums 1 through 5 according to the firstthrough fifth embodiment of the present invention are explained above.With referring to FIG. 33, a first reproducing apparatus for reproducingany of the information recording mediums 1 through 5 is explained next.The information recording medium 1 represents the information recordingmediums 1 though 5 generically for simplifying the explanationhereinafter.

FIG. 33 is a block diagram of a first reproducing apparatus forreproducing an information recording medium according to the presentinvention. As shown in FIG. 33, a first reproducing apparatus 40 is anapparatus for reproducing a recording layer 12 of the informationrecording medium 1 and composed of at least a reproducing unit providedwith a light emitting element, which emits reproducing light having awavelength λ of 350 nm to 450 nm and has a noise level of less than RIN−125 dB/Hz, and an objective lens having a numerical aperture NA of 0.75to 0.9, and a control unit, which controls the reproducing unit so as toreproduce the information recording medium 1 by irradiating thereproducing light only on a land portion “L” of the informationrecording medium 1.

Actually, the first apparatus 40 is at least composed of a pickup 50 forreading reflected light from the information recording medium 1, a motor51 that rotates the information recording medium 1, a servo controller52 for controlling to drive the pickup 50 and the motor 51, a turntable53 for supporting the information recording medium 1 while rotating, ademodulator 54 for demodulating an information signal that is read outby the pickup 50, an interface (I/F) 55 for outputting a signal that isdemodulated by the demodulator 54, and a controller 60 that controls thefirst reproducing apparatus 40 totally.

The demodulator 54 hereupon is a digital converter that returns 16-bitdata to original 8-bit data if a reproduced signal is modulated by theEFM plus modulation (8-16 modulation) method, which is commonly used forthe DVD system.

The turntable 53 and the information recording medium 1 is connectedwith plugging a center hole Q of the information recording medium 1 withthe turntable 53. Such a connection between the turntable 53 and theinformation recording medium 1 can be either a fixed connection orsemi-fixed connection, which can load or release the informationrecording medium 1 freely.

Further, the information recording medium 1 can be contained in acartridge. With respect to a cartridge, a commonly known cartridgehaving an opening and closing mechanism in the center can be used as itis.

The motor 51 is linked to the turntable 53 and the turntable 53 isplugged with the center hole Q of the information recording medium 1.

Further, the motor 51 supports the information recording medium 1 andsupplies relative motion for reproduction to the information recordingmedium 1 through the turntable 53. A signal output can be supplied to anot shown external output terminal or directly supplied to a not showndisplay device, audio equipment or printing equipment.

The pickup 50 is at least composed of a light emitting element 50 a,which emits light having a single wavelength λ within a range of 350 nmto 450 nm, desirably 400 nm to 435 nm, an objective lens 50 b having anumerical aperture NA within a range of 0.75 to 0.9, and a photodetector 9, which receives reflected light that is reflected by theinformation recording medium 1 although they are not shown in FIG. 33.

Further, the pickup 50 forms reproducing light 99 in conjunction withthese components. It is acceptable that the light emitting element 50 ais a semiconductor laser of gallium nitride system compound or a laserhaving a second harmonic generating element.

Furthermore, the servo controller 52 is indicated only one in FIG. 33.However, it can be divided into two; one is a driving control servo forthe pickup 50 and the other is another driving control servo for themotor 51.

With respect to the demodulator 54, a commonly know equalizer and thePRML (partial response maximum likelihood) decoding circuit, which arenot shown, can be installed in the demodulator 54. With respect to anequalizer (waveform equalizer), for example, a so-called neural netequalizer (that is disclosed in the Japanese Patent No. 2797035) inwhich a plurality of conversion systems having a nonlinear input-outputcharacteristic is combined together with applying individual variableweighting and constitutes a neural network, a so-called limit equalizer(that is disclosed in the Japanese Patent Application Laid-openPublication No. 11-259985/1999) in which an amplitude level ofreproduced signal is limited to a predetermined value and forwarded to afiltering process, and a so-called error selection type equalizer (thatis disclosed in the Japanese Patent Application Laid-open PublicationNo. 2001-110146) in which an error between a reproduced signal and anobjective value for waveform equalization is obtained and a frequency ofthe waveform equalizer is changed adaptively so as to minimize the errorcan be preferably used.

Moreover, in the commonly known PRML decoding circuit that contains apredicted value controlling and equalization error calculating circuit,a so-called adaptive viterbi decoder (that is disclosed in the JapanesePatent Application Laid-open Publications No. 2000-228064 and No.2001-186027) in which a predicted value utilized for decoding viterbialgorithm is calculated and a frequency response is optimized so as tominimize an equalization error of waveform equalizer can be usedparticularly.

Operations of the first apparatus 40 are explained next. The reproducinglight 99 is emitted from the light emitting element 50 a of the pickup50 through the objective lens 50 b and converged on the microscopicpattern 21 of the information recording medium 1 loaded on the turntable53.

Accurately, the reproducing light 99 is focused on the microscopicpattern 21 that is disposed at a depth of 0.07 mm to 0.12 mmcorresponding to the thickness of the light transmitting layer 11.Succeedingly, the reproducing light 99 tracks either a groove portion“G” or a land portion “L”. The tracking is conducted on a predeterminedportion of either the groove portion “G” or the land portion “L”.However, as mentioned above, selecting the land portion “L” is mostdesirable.

The reflected light from the microscopic pattern 21 is received by thephoto detector 9 not shown and a recorded signal is read out. As shownin FIG. 10, the photo detector 9 is divided into four sections. A totalsum signal, that is, “(Ia+Ib+Ic+Id)” of outputs from the divided foursections of the photo detector 9 (hereinafter referred to as “4-divisionphoto detector” 9) is transmitted to the demodulator 54. Reading out therecorded signal is conducted by reproducing a record mark “M” that isrecorded only on the land portion “L”, for example, in the microscopicpattern 21 as shown in FIG. 3.

It is omitted in the above explanation that a focus error signal isnecessary for focusing to be generated and a tracking error signal isnecessary for tracking to be generated. Such a focus error signal and atracking error signal is generated by a differential signal in theradial direction, that is, “(Ia+Ib)−(Ic+Id)”, which is outputted fromthe 4-division photo detector 9, and transmitted to the servo controller52. In the servo controller 52, a focus servo signal or a tracking servosignal is produced from the received focus error signal or the trackingerror signal in accordance with controlling by the controller 60, thenthe focus servo signal or the tracking servo signal is transmitted tothe pickup 50.

In addition thereto, a rotary servo signal is produced in the servocontroller 52 and transmitted to the motor 51.

Further, in the demodulator 54, the recorded signal is demodulated andapplied with error correction as required, and a data stream that isobtained is transmitted to the I/F 55. Finally, a signal is outputtedexternally in accordance with controlling by the controller 60.

As mentioned above, the first reproducing apparatus 40 of the presentinvention is loaded with an information recording medium 1 and designedfor coping with the reproducing light 99, which is generated by thelight emitting element 50 a (not shown) having single wavelength λwithin the range of 350 nm to 450 nm, the objective lens 50 b (notshown) having the numerical aperture NA of 0.75 to 0.9 and the4-division photo detector 9 (not shown). Therefore, the firstreproducing apparatus 40 can reproduce the information recording medium1 excellently.

Accordingly, the first reproducing apparatus 40 is such a reproducingapparatus that reads out information recorded on the recording layer 12(or 123). Particularly, the first reproducing apparatus 40 can reproducecontents, which are continuously recorded for a long period of time, andcan be used for reproducing an HDTV program and a movie, which arerecorded by video equipment, for example.

With referring to FIG. 34, a second reproducing apparatus forreproducing any of the information recording mediums 1 through 5according to the present invention is explained, wherein the informationrecording medium 1 represents the information recording mediums 1 though6 generically for simplifying the explanation hereinafter.

FIG. 34 is a block diagram of a second reproducing apparatus forreproducing an information recording medium according to the presentinvention. In FIG. 34, a second reproducing apparatus 41 is identical tothe first reproducing apparatus 40 except for an auxiliary informationdemodulator 56 and a reference clock demodulator 57, which are providedbetween the pickup 50 and the controller 60 and demodulate an auxiliaryinformation and a reference clock read out by the pickup 50respectively. The second reproducing apparatus 41 is a reproducingapparatus that is used for index reproduction of a HDTV program and amovie, which are recorded by video equipment, and for index reproductionof data stored in a computer.

As mentioned above, a signal that is transmitted from the pickup 50 tothe demodulator 54 is the total sum signal, that is, “(Ia+Ib+Ic+Id)”outputted form the 4-division photo detector 9 not shown. In addition,another signal that is transmitted from the pickup 50 to the auxiliaryinformation demodulator 56 is the differential signal in the radialdirection, that is, “(Ia+Ib)−(Ic+Id)” outputted from the 4-divisionphoto detector 9 not shown.

An auxiliary information and a reference clock recorded geometrically inthe information recording medium 1 as a wobbling groove. The wobbling isformed in the radial direction, so that the auxiliary information andthe reference clock can be extracted by monitoring the differentialsignal.

With respect to an actual constitution of the auxiliary informationdemodulator 56, it is constituted by at least any one of anamplitude-shift keying modulation demodulator, a frequency-shift keyingmodulation demodulator and a phase-shift keying modulation demodulator.

More accurately, an envelope detector circuit can be suitably used forthe amplitude-shift keying modulation demodulator. A frequency detectorcircuit and a synchronous detector circuit can be suitably used for thefrequency-shift keying modulation demodulator. A synchronous detectorcircuit, a delay detector circuit and an envelope detector circuit canbe suitably used for the phase-shift keying modulation demodulator.

The amplitude-shift keying modulation wave 250, the frequency-shiftkeying modulation wave 260 or the phase-shift keying modulation wave270, which constitutes the auxiliary signal area 200, is inputted to theauxiliary information demodulator 56 and an auxiliary information isdemodulated from the differential signal in the radial directionoutputted from the 4-division photo detector 9.

The total sum signal may leak into the differential signal in the radialdirection although it may be a small amount. In order to avoid suchleaking, a band-pass filter that is adjusted for a frequency range of anauxiliary signal can be inserted between the pickup 50 and the auxiliaryinformation demodulator 56.

An actual constitution of the reference clock demodulator 57 is at leastcomposed of a slicing circuit. The single-frequency wave 350, whichconstitutes the reference clock area 300 and is extracted from thedifferential signal in the radial direction that is outputted from the4-division photo detector 9, is inputted to the reference clockdemodulator 57. In the reference clock demodulator 57, thesingle-frequency wave 350 is properly sliced and formed in binary coded.In order to separate the single-frequency wave 350 from a signalobtained from the auxiliary signal area 200, a band pass filter can beinserted into a previous stage immediately before the reference clockdemodulator 57. A binary coded Signal controls revolution of the motor51 through the controller 60 and the servo controller 52 in order todecide a number of revolutions of the turntable 53.

Further, in order to amplify, wave-transform, wave-shape orfrequency-divide the binary coded signal, an amplifier, a waveformtransformer, a waveform shaper, or a frequency divider can be connectedto the second reproducing apparatus 41 additionally.

The auxiliary information demodulator 56 and the reference clockdemodulator 57 is connected so as to distribute the differential signalrespectively. A switching circuit not shown can be inserted in aprevious stage before the auxiliary information demodulator 56 and thereference clock demodulator 57 in order not to deteriorate S/N and inorder to reduce reading out error. In case that the auxiliaryinformation area 200 and the reference clock area 300 is allocated atevery predetermined interval, prediction for a following signal to beread out can be theoretically decided by reading out and identifying thesignal. Consequently, the switching circuit can be constituted.

Furthermore, in case that a start bit signal and a stop bit signal isallocated between the auxiliary information area 200 and the referenceclock area 300, prediction for a following signal to be read out can betheoretically decided by referring to these start bit and stop bitsignals. Consequently, the switching circuit can be theoreticallyconstituted.

With referring to FIGS. 34 and 35, an operation of the secondreproducing apparatus 41 is explained next.

FIG. 35 is a flow chart showing a method for reproducing according to anembodiment of the present invention. As shown in FIG. 35, an operationof the second reproducing apparatus 41, that is, a method of reproducingthe information recording medium 1 by using the second reproducingapparatus 41 is composed of at least following steps. The informationrecording medium 1 is loaded on the turntable 53 of the secondreproducing apparatus 41 (step P1). The reproducing light 99 from thepickup 50 is converged and focused on the microscopic pattern 21 formedin the information recording medium 1 (step P2), and is made tracking(step P3). A differential signal is produced from reflected reproducinglight 99 that is reflected by the microscopic pattern 21 (step P4). Areference clock signal is extracted from the differential signal (stepP5). Revolution of the motor 51 is controlled by the extracted referenceclock signal (step P6). An auxiliary information is extracted from thedifferential signal (step P7). An address information is extracted fromthe extracted auxiliary information (step P8). A position of the pickup51 is controlled by the extracted address information and an addressinformation inputted externally (step P9). A total sum signal isdemodulated and reproduced (step P10).

More specifically, the information recording medium 1 is loaded on theturntable 53, which can control revolution of the information recordingmedium 1 to the circumferential direction (the step P1). Succeedingly,the reproducing light 99 is emitted from the light emitting element 50 aof the pickup 50 through the objective lens 50 b and converged on themicroscopic pattern 21 of the information recording medium 1 (the stepP2). Accurately, the reproducing light 99 is focused on the microscopicpattern 21, which is disposed at a depth of 0.07 mm to 0.12 mm that isequivalent to the thickness of the light transmitting layer 11. Then,the reproducing light 99 is conducted to a track either the grooveportion “G” or the land portion “L” (the step P3). The tracking isconducted by selecting a portion previously decided. However, asmentioned above, selecting the land portion “L” is most preferable. Thedifferential signal “(Ia+Ib)−(Ic+Id)” in the radial direction isproduced from reflected light that is reflected by the microscopicpattern 21 and picked up by the pickup 50 (the step P4). The produceddifferential signal is transmitted to the reference clock demodulator 57and a clock signal is produced (the step P5).

Further, the clock signal is transmitted to the controller 60 so as tocontrol a number of revolutions of the turntable 53 and controlsrevolution of the motor 51 by way of the servo controller 52 (the stepP6).

The differential signal is transmitted to the auxiliary informationdemodulator 56 at the same time, and an auxiliary information is readout (the step P7). At this moment, an address information out of variousauxiliary information is extracted from the extracted auxiliaryinformation (the step P8). The extracted address information is comparedwith another address information that is utilized for indexing datainputted to the controller 60. In case that the extracted addressinformation does not coincide with the other address information, thecontroller 60 sends a signal to the servo controller 52 and instructsthe servo controller 52 to search. The searching is conducted such thata number of revolutions of the motor 51 is reset to a specific number ofrevolutions, which corresponds to a radius between the motor 51 and thepickup 50, according to movement in the radial direction of the pickup50 while scanning the movement of the pickup 50 in the radial direction.

Furthermore, during a process of scanning, an address informationoutputted from the address information demodulator 56, which receivesthe differential signal from the pickup 50, is compared with apredetermined address information. The searching is continued until theycoincide with each other (the step P9). When they coincide, scanning inthe radial direction is interrupted and reproduction is switched over tocontinuous reproduction of the total sum signal “(Ia+Ib+Ic+Id)” (thestep P10). An output from the demodulator 54 in which the total sumsignal “(Ia+Ib+Ic+Id)” is inputted, is resulted in demodulating a datastream that is obtained by indexing, and the output is inputted to theI/F 55. Finally, the I/F 55 outputs a signal externally in accordancewith controlling conducted by the controller 60.

As mentioned above, according to the second reproducing apparatus 41 andthe reproducing method that is composed of the steps P1 through P10 ofthe present invention, an information recording medium 1 is loaded on.

Further, the second reproducing apparatus 41 and the reproducing methodis designed for coping with the reproducing light 99, which is generatedby the light emitting element 50 a having a single wavelength λ withinthe range of 350 nm to 450 nm and the objective lens 50 b having thenumerical aperture NA of 0.75 to 0.9. Therefore, the second reproducingapparatus 41 and the reproducing method can suitably reproduceinformation that is recorded in the recording layer 12 of theinformation recording medium 1. At the same time, they can perform indexreproduction of a data stream by reproducing an auxiliary informationthereto.

Furthermore, in case that an auxiliary information contains informationrelated to reproduction laser power other than an address information,it is acceptable for a power value of the light emitting element 50 a tobe set or to be renewed by extracting the information related toreproduction laser power from the read-out auxiliary information.

An NA of the objective lens 50 b is large, so that spherical aberrationcaused by thickness error of the light transmitting layer 11 of theinformation recording medium 1 becomes extremely large. Consequently,spherical aberration is compensated by adjusting an optical system inthe pickup 50. Actually, in the step P2, for example, the sphericalaberration can be compensated by adjusting the optical system tomaximize an output of differential signal after focusing. If acorrective lens not shown is installed in the pickup 50, for example, itis possible to find a maximum point of differential signal by changing adistance between the corrective lens and another optical element such asthe objective lens 50 b.

Further, compensating spherical aberration can be conducted by observinga total sum signal. More specifically, in the step P10, the compensationcan be realized by adjusting an optical system as mentioned above suchthat an output of the total sum signal is adjusted to be maximal.

With respect to spherical aberration that is compensated by observing adifferential signal, it is also acceptable for compensation to beconducted by observing a differential signal of a microscopic patternthat is disposed in a predetermined specific area.

Further, in case that spherical aberration is compensated by observing atotal sum signal, it is also acceptable that test data is recorded on aland portion “L” or a groove portion “G” in a predetermined specificarea and the compensation is conducted by observing a total sum signalof the test data. Particularly, in case that the information recordingmedium 1 is in disciform, these compensating methods of sphericalaberration are desirable to be performed in an area, where a user neverrecords or reproduces data, such as an area allocated in the innercircumference area.

With referring to FIG. 36, a recording apparatus for recording any ofthe information recording mediums 1 through 5 according to the presentinvention is explained, wherein the information recording medium 1represents the information recording mediums 1 though 5 generically forsimplifying the explanation hereinafter.

FIG. 36 is a block diagram of a recording apparatus 90 for recording aninformation recording medium 1 according to the present invention. Therecording apparatus 90 is an apparatus for recording information in therecording layer 12 of the information recording medium 1, and composedof at least a recording unit provided with a light emitting element,which emits recording light having a wavelength λ of 350 nm to 450 nmand has a noise level of less than RIN −125 dB/Hz, and an objective lenshaving a numerical aperture NA of 0.75 to 0.9, and a control unit, whichcontrols the recording unit so as to record the information recordingmedium 1 by irradiating the recording light exclusively on a landportion “L” of the information recording medium 1.

Actually, the recording apparatus 90 is similar to the secondreproducing apparatus 41 shown in FIG. 34 except for followings: thedemodulator 54 is replaced by a modulator 82 for modulating an originaldata and a waveform converter 83 for transforming a modulated signalfrom the modulator 82 into a waveform suitable for recording on aninformation recording medium 1, which are connected in series, and theI/F 55 is replaced by an interface (I/F) 81 for receiving an externalsignal to be recorded. Other components are exactly the same as those ofthe second reproducing apparatus 41, so that explanations for the samefunctions and operations are omitted.

Further, the recording apparatus 90 is an apparatus for recording acomputer data, for example, at a predetermined address newly orrecording a HDTV program or a movie continuously from a predeterminedaddress by a video recorder.

The modulator 82 is such a modulator that converts an 8-bit originaldata into 16 bits, in case of the EFM plus modulation method. Thewaveform converter 83 transforms a modulated signal that is receivedfrom the modulator 82 into another waveform that is suitable forrecording on an information recording medium 1. Actually, the waveformconverter 83 is such a converter that converts a modulated signal into arecording pulse, which satisfies a recording characteristic of therecording layer 12 of the information recording medium 1. In case thatthe recording layer 12 is composed of a phase change material, forexample, a so-called multi-pulse is formed. In other words, themodulated signal is divided into a unit of channel bit or less than theunit of channel bit, and recording power is changed into a rectangularwaveform, wherein peak power, bottom power, erase power and a pulse timeduration, which constitute a multi-pulse, are adjusted in accordancewith a direction of the controller 60.

With referring to FIGS. 36 and 37, an operation of the recordingapparatus 90 is explained next.

FIG. 37 is a flow chart showing a recording method of an informationrecording medium 1 by using the recording apparatus 90 shown in FIG. 36.As shown in FIG. 37, an operation of the recording apparatus 90, thatis, a recording method of the information recording medium 1 by usingthe recording apparatus 90 is composed of at least following steps. Theinformation recording medium 1 is loaded on the turntable 53 of therecording apparatus 90 (step R1). The reproducing light 99 from thepickup 50 is converged and focused on the microscopic pattern 20 formedin the information recording medium 1 (step R2), and is made tracking(step R3). A differential signal is produced from reflected reproducinglight 99 that is reflected by the recording later 12 (step R4). Areference clock signal is extracted from the differential signal (stepR5). Revolution of the motor 51 is controlled by the extracted referenceclock signal (step R6). An auxiliary information is extracted from thedifferential signal (step R7). An address information is extracted fromthe extracted auxiliary information (step R8). A position of the pickup50 is controlled by the extracted address information and anotheraddress information inputted externally (step R9). An inputted signal isdemodulated and the recording light 89 is emitted (step R10).

More specifically, the information recording medium 1 is loaded on theturntable 53 that can control revolution of the information recordingmedium 1 to the circumferential direction (the step R1). Succeedingly,the reproducing light 99 is emitted from the light emitting element 50 aof the pickup 50 through the objective lens 50 b and converged on themicroscopic pattern 20 of the information recording medium 1 (the stepR2). More accurately, the reproducing light 99 is focused on themicroscopic pattern 20, which is disposed at a depth of 0.07 mm to 0.12mm that is equivalent to the thickness of the light transmitting layer11. Then, the reproducing light 99 is conducted to a track either thegroove portion “G” or the land portion “L” (the step R3). The trackingis conducted by selecting a portion previously decided. However, asmentioned above, selecting the land portion “L” is most preferable. Thedifferential signal “(Ia+Ib)−(Ic+Id)” in the radial direction isproduced from reflected reproducing light 99 that is reflected by therecording layer 12 and picked up by the pickup 50 (the step R4). Theproduced differential signal is transmitted to the reference clockdemodulator 57 and a clock signal is produced (the step R5).

Further, the clock signal is transmitted to the controller 60 so as tocontrol a number of revolutions of the turntable 53 and controlsrevolution of the motor 51 by way of the servo controller 52 (the stepR6).

The differential signal is transmitted to the auxiliary informationdemodulator 56 at the same time, and an auxiliary information is readout (the step R7). At this moment, an address information out of variousauxiliary information is extracted (the step R8). The extracted addressinformation is compared with another address information that isutilized for indexing data, which is inputted to the controller 60. Incase that the extracted address information does not coincide with theother address information, the controller 60 sends a signal to the servocontroller 52 and instructs the servo controller 52 to search. Thesearching is conducted such that a number of revolutions of the motor 51is reset to a specific number of revolutions, which corresponds to aradius between the motor 51 and the pickup 50, according to movement inthe radial direction of the pickup 50 while scanning the movement of thepickup 50 in the radial direction.

Furthermore, during a process of scanning, an address informationoutputted from the address information demodulator 56, which receives adifferential signal from the pickup 50, is compared with a predeterminedaddress information. The searching is continued until they coincide witheach other (the step R9). When they coincide with each other, scanningin the radial direction is interrupted and reproduction is switched overto a recording operation. In other words, data inputted form the I/F 81is demodulated by the demodulator 82 in accordance with controllingconducted by the controller 60. The modulated data is inputted into thewaveform converter 83 in accordance with the controlling conducted bythe controller 60 and finally, the demodulated data is transformed intoa format that is suitable for recording, and outputted to the pickup 50(the step R10).

In the pickup 50, the recording light 89 is generated by changingrecording power to a predetermined recording power that is designated bythe waveform converter 83, and irradiated on the information recordingmedium 1. Consequently, the original data is recorded at a predeterminedaddress in the information recording medium 1.

In addition thereto, the recording light 89 can read out thedifferential signal “(Ia+Ib)−(Ic+Id)” in the radial direction and anaddress can be extracted from the auxiliary information demodulator 56even while recording. Accordingly, limited area recording as far as anaddress that is required by a user can be conducted.

As mentioned above, according to the recording apparatus 90 and therecording method that is composed of the steps R1 through R10 of thepresent invention, an information recording medium 1 is loaded on.

Further, the recording apparatus 90 and the recording method is designedfor coping with the reproducing light 99 and the recording light 89,which are generated by the light emitting element 50 a having a singlewavelength λ within the range of 350 nm to 450 nm and the objective lens50 b having the numerical aperture NA of 0.75 to 0.9. Therefore, therecording apparatus 90 and the recording method can suitably recordinformation in the recording layer 12 of the information recordingmedium 1. At the same time, they can reproduce even auxiliaryinformation and can conduct random indexing for recording.

Furthermore, in case that an auxiliary information contains informationrelated to recording strategy for generating multi-pulse such as peakpower, erase power, and pulse interval other than an addressinformation, it is acceptable that a setting value of the waveformconverter 83 is designated or renewed by extracting these strategicinformation from the read-out auxiliary information.

More, it is possible to combine the above-mentioned recording method andthe reproducing method together. For example, an additional step ofconfirming whether or not recording on an information recording medium 1is conducted correctly by reproducing the recorded information recodingmedium 1 can be added after the information recording medium 1 isrecorded by the recording method that is composed of the steps R1through R10. The additional step of confirming is conducted byreproducing the recorded area by the reproducing light 99, and bycomparing data to be recorded and another data to be reproduced.

Moreover, by extracting an address information from an auxiliaryinformation, the additional step of confirming can be compared with theaddress information hereat. In case that data not recorded properly isfound by the comparing, an address information corresponding to theoriginal data is recorded in a specific area at the inner circumferencearea and/or the outer circumference area of the information recordingmedium 1. In other words, in case that an error is found when confirmingby reproducing after recording, the address information is recorded in aspecific area of the information recording medium 1. Consequently, anaddress information having error can be recognized by referring to thespecific area when reproducing data recorded by a user.

Further, it is possible to reproduce the recorded data excluding onlydata corresponding to the address information.

Accordingly, reproduction without error can be enabled.

Furthermore, in case that data not recorded properly is found by thecomparing, it is acceptable that the defective data is recorded inanother area having another address information together with recordingan address information corresponding to the original data in a specificarea at the inner circumference area and/or the outer circumference areaof the information recording medium 1. By this process, not onlyreproducing without error but also compensating a defective part can beconducted, so that it is more effective.

The light emitting element 50 a that is used in the first and secondreproducing apparatuses 40 and 41 is detailed hereupon. The lightemitting element 50 a is defined as either a semiconductor laser ofgallium nitride system compound or a laser having a second harmonicgenerating element. However, these individual laser elements have aparticular laser noise respectively. In the case of a semiconductorlaser of gallium nitride system compound, particularly, its noise levelis relatively high. According to our measurement for the noise level, alaser RIN (Relative Intensity Noise) of a laser having a second harmonicgenerating element is −134 dB/Hz that is a similar noise level to thatof a red-light emitting semiconductor laser having a wavelength of 650nm approximately being used for a DVD system.

On the other hand, in case of a semiconductor laser of gallium nitridesystem compound, its laser RIN is −125 dB/Hz. That is, the laser RIN ofthe semiconductor laser of gallium nitride system compound is largerthat that of the laser having a second harmonic generating element by 9dB. The noise is added to a reproduced signal from the informationrecording medium 1 and results in deteriorating an S/N of the reproducedsignal extremely. In other words, in case that a semiconductor laser ofgallium nitride system compound is adopted for the light emittingelement 50 a of the first and second reproducing apparatuses 40 and 41,a signal characteristic is deteriorated. Therefore, a guide fordesigning DVD system that has been obtained by us can not be applied forthe first and second reproducing apparatuses 40 and 41 by just shiftingthe guide proportionally.

Accordingly, in view of that a particular noise inherent in a laser isadded to a reproduced signal from the information recording medium 1when reproduced by these first and second reproducing apparatuses 40 and41, it is essential for an information recording medium to have a signalcharacteristic in which a worsen component caused by the particularnoise inherent in a laser is compensated.

With respect to the information recording medium 5 according to thefifth embodiment of the present invention, by changing a depth of themicroscopic pattern 20, that is, height difference between a grooveportion “G” and a land portion “L” formed on the substrate 13, severalvariations of the information recording medium 5 are manufactured. Thoseinformation recording mediums are reproduced by the second reproducingapparatus 41 that is installed with a semiconductor laser of galliumnitride system compound having a laser RIN of −125 dB/Hz as the lightemitting element 50 a, and a relation between reflectivity and an errorrate of reproduced signal is studied.

In addition thereto, recording is conducted by the recording apparatus90 under an ideal recording condition such that an error rate decreasesmaximally.

Reflectivity could be defined as an output of reproduced signal. In casethat the recording layer 123 is constituted by a phase change material,reflectivity is an index correlating to brightness of the recordinglayer 123 in a crystalline state. More specifically, an informationrecording medium 5 is recorded with a modulation signal of theabove-mentioned (d, k) code. The information recording medium 5 isloaded in the second reproducing apparatus 41 so as to be flat orwithout declining, and then a recorded signal is reproduced. Thereproduced signal of a DC system outputted from the pickup 50 isconnected to an oscilloscope, and reflectivity is obtained from a signalhaving the maximum mark length (k+1). In the case of the 17 PPmodulation, for example, in which “d” and “k” is “one” and “seven”respectively, a minimum mark length (d+1) is 2T and a maximum marklength (k+1) is 8T. Therefore, reflectivity is calculated from anabsolute reflectivity calibration line by measuring I8H.

Further, an error rate is obtained by measuring a reproduced signalobtained through the demodulator 54.

Result of measuring modulated amplitude and error rate by the secondreproducing apparatus 41 after recording the 17PP modulation by therecording apparatus 90 is shown in FIG. 38.

FIG. 38 is a graph exhibiting a relation between reflectivity and errorrate. As shown in FIG. 38, there is existed an apparent mutual relationbetween reflectivity and error rate. It is apparent that an error ratedrastically increases in accordance with reflectivity that decreases. Incase that a practical error rate is defined as 3×10⁻⁴ that is the figurespecified by the several standards such as the DVD Standard, necessaryreflectivity is more than 2%.

Further, the information recording medium 5 may warp by temperaturechange in the surrounding of use. Consequently, with assuming that theinformation recording medium 5 inclines by the order of 0.7 degree asthe same angle as a DVD disc, an error rate increases more than comaaberration caused compositively by conditions such that a wavelength λis within a range of 350 nm to 450 nm, a numerical aperture NA is withina range of 0.75 to 0.9, and a thickness of the light transmitting layer11 is within a range of 0.07 mm to 0.12 mm.

Furthermore, in case that the information recording medium 5 is inclinedby 0.7 degree, it is found by an experimental measurement that the errorrate of 3×10⁻⁴ is equivalent to 0.7×10⁻⁴ when the incline is zerodegree. In other words, the error rate of 0.7×10⁻⁴ is essential foractual use.

Accordingly, it is found that practical reflectivity is more than 5%.

As mentioned above, in the case that the semiconductor laser of galliumnitride system compound is used as a light emitting element, a noise isadded to a reproduced signal. Therefore, by constituting reflectivity ofthe information recording medium 5 to be more than 5%, an error rate canbe practically reduced to the same degree as the DVD Specification.

Further, it is found by an experimental study that the correlationbetween reflectivity and error rate shown in FIG. 38 can be obtained byany of the modulation methods mentioned above. It is caused by that asignal output almost saturates in any modulation methods when themaximum mark length (k+1) exceeds 6T approximately and becomes aconstant value although the maximum mark length (k+1) varies by themodulation methods.

Accordingly, one reflectivity obtained by recording the informationrecording medium 1 by the 17PP modulation method, wherein “d” is one and“k” is seven, is a same value as the other reflectivity obtained by theEFM plus modulation method, wherein “d” is two and “k” is ten. In theabove-mentioned case, if the information recording medium 1 is replacedby the information recording medium 5, the same result is obtained.

In consideration of the reproducing characteristic of the first andsecond reproducing apparatuses 40 and 41 and the recording apparatus 90,the information recording mediums 1 through 5 according to the presentinvention of which reflectivity is designated to be more than 5% areexplained above.

In consideration of a general characteristic of the first and secondreproducing apparatuses 40 and 41 and the recording apparatus 90 ofwhich light emitting element is constituted by a semiconductor laser ofgallium nitride system compound, and a physical characteristic of therecording layer 12 or 123, which is constituted by a phase changematerial, totally, a range of more practical reflectivity of theinformation recording mediums 1 through 5 that is necessary forrealizing a total system is explained next.

A maximal output of semiconductor laser of gallium nitride systemcompound is merely 30 mW. In a recording apparatus, it is general thatan output of a pickup decreases almost one fifth of a laser output dueto a coupling efficiency of optical elements applied for a wavelength λwithin a range of 350 nm to 450 nm. In other words, a laser powerdecreases down to 6 mW on the surface of the information recordingmediums 1 through 5 although a laser of which output is 30 mW is used.

On the contrary, in order to realize phase change recording in excellentcontrast, a recording power is desirable to be designated as high aspossible. Therefore, the information recording mediums 1 through 5 areessential to be recorded by the recording power of the order of 6 mW.Consequently, an absorbency index and transmittance of the recordinglayer 12 or 123 of the information recording mediums 1 through 5 isessential to be a higher value relatively.

A particular noise inherent in a semiconductor laser of gallium nitridesystem compound and increasing noise in a reproducing apparatusutilizing the semiconductor laser of gallium nitride system compound ismentioned above. However, it is also necessary to pay attention to thata noise depends upon a reproduction laser power when designing a totalsystem. The inventors of the present invention measure a laser noisewhile changing a reproduction laser power. In case of a semiconductorlaser of gallium nitride system compound, it is found that a noiseincreases in accordance with a laser power that decreases, and foundparticularly that there is existed a critical point at 0.35 mW of laserpower on a surface of information recording medium. In other words, whenthe laser power is lower than 0.35 mW, a noise increases extremely.Consequently, a reproduction laser power on the surface of theinformation recording mediums 1 through 5 is essential to be more than0.35 mW.

With respect to a physical characteristic of the recording layer 12 or123, there is existed a phenomenon such that the recording layer 12 or123 is damaged thermally and a recorded record mark “M” vanishes when areproduction laser power is increased. Accordingly, it is necessary fora reproduction laser power to be set to lower than a particular value.Particularly, in case of reproducing light having a wavelength λ withina range of 350 nm to 450 nm, an energy density of a spot “S” formed on asurface of recording layer is larger than that of a red-light emittingsemiconductor laser of which wavelength is within a range of 635 nm to830 nm, for example. Therefore, a reproduction laser power is setrelatively low. However, a permissible range of reproduction laser poweris narrowed due to the above-mentioned minimum limit for reproductionlaser power. In order to increase tolerance for reproduction laserpower, that is, in order to set a reproduction laser power larger, anabsorbency index and transmittance of the recording layer 12 or 123 ofthe information recording mediums 1 through 5 is essential to be a lowervalue relatively.

As mentioned above, in consideration of the general characteristic ofthe first and second reproducing apparatuses 40 and 41 and the recordingapparatus 90 of which light emitting element is constituted by asemiconductor laser of gallium nitride system compound, and the physicalcharacteristic of the recording layer 12 or 123, which is constituted bya phase change material, totally, it is concluded that an informationrecording medium in which a record mark “M” on the recording layer 12 or123 is hardly vanished by a reproduction laser power of more than 0.35mW is required while a recording power is in the neighborhood of 6 mW.In other words, an absorbency index and transmittance is essential to bewithin a predetermined range. A sum of an absorbency index andtransmittance and reflectivity is one, so that reflectivity is essentialto be within a predetermined range as well.

The inventors of the present invention experimentally study areflectivity range that satisfies the above-mentioned limitations, andfind an optimal reflectivity range of 12% to 26%. Hereinafter, an actualmanufacturing process of the information recording medium 5 is detailedas embodiments 1 through 7 and comparative examples 1 and 2.

Embodiments 1 through 7

FIG. 39 is a chart exhibiting reflectivity and reproductioncharacteristics of embodiments 1 through 7 and comparative examples 1and 2.

Samples of embodiments 1 through 7 and comparative examples 1 and 2 aremanufactured as a phase-change recording type information recordingmedium 5. A polycarbonate plate having a thickness of 1.1 mm is utilizedfor a substrate 13. A reflective layer 121, a first protective layer122, a recording layer 123, and a second protective layer 124 isconstituted by Ag₉₈Pd₁Cu₁, ZnS—SiO₂ (80:20 at mol %), Ge_(s)Sb₆₉Te₂₃,and ZnS—SiO₂ (80:20 at mol %) respectively, wherein each film thicknessof the reflective layer 121, the first protective layer 122, therecording layer 123, and the second protective layer 124 follows figuresshown in FIG. 39 respectively. Finally, a polycarbonate plate having athickness of 0.10 mm is laminated on the second protective layer 124.Consequently, the samples of the embodiments 1 through 7 and thecomparative examples 1 and 2 are completed as an information recordingmedium 5.

An auxiliary information area 200 and a reference clock area 300 isformed continuously on a land portion “L” of each information recordingmedium 5 without being interrupted. The auxiliary information area 200is composed of a frequency-shift keying modulation wave 262 of whichfundamental wave is a sinusoidal wave (or a cosine wave), wherein aphase difference between a higher frequency section and a lowerfrequency section is “2π±(π/2.5)”.

Further, a phase is selected so as to be that the waveform continues ata point where a frequency changes over from higher to lower or viceversa.

Furthermore, the auxiliary information area 200 is recordedgeometrically on a sidewall as a wobbling groove.

In addition thereto, a single-frequency wave 350 of which fundamentalwave is a sinusoidal wave (or a cosine wave) is recorded geometricallyon a sidewall as a wobbling groove.

The information recording medium 5 is designed for recording orreproducing by using a pickup installed with optical elements of whichwavelength λ is 405 nm and an NA is 0.85, and a pitch “P” between landportions “L” is 0.32 μm.

Further, the reflective layer 121 and the recording layer 123 is formedby the DC sputtering process, and the first and second protective layers122 and 124 are formed by the AC sputtering process in an atmosphere ofargon gas of 5 mTorr.

Furthermore, a vacuum chamber used for sputtering is sufficientlyexhausted as low as less than 1×10⁻⁶ Torr.

More, each completed information recording medium 5 is initialized byirradiating a laser beam on the recording layer 123 through the lighttransmitting layer 11, and the recording layer 123 is phase-changed froman amorphous state in lower reflectivity to a crystalline state inhigher reflectivity.

Each information recording medium 5 is loaded on the recording apparatus90 equipped with a pickup installed with optical elements of whichwavelength λ is 405 nm and an NA is 0.85. A recording signal is recordedon a land portion “L” with a modulation signal of which minimum marklength (equal to 2T) is designated to be 0.149 μm by the 17PP modulationmethod, wherein “d” and “k” is “one” and “seven” respectively.

Further, a differential signal reproduced from the reference clock area300 of each information recording medium 5 is transmitted to thereference clock demodulator 57 and revolution of the turntable 53 iscontrolled by the obtained reference clock. By controlling the turntable53 as mentioned above, a record mark “M” having a desired length isconducted to be recorded accurately. With respect to a recordingcondition, a recording peak power is 6.0 mW, a bias power is 2.6 mW, abottom power between multi-pulses and a cooling pulse is 0.1 mW, and alinear velocity is 5.3 m/s respectively.

Furthermore, the recording is conducted by a signal, which istransformed into a so-called multi-pulse by the waveform converter 83,and by adopting a 3-level power modulation method, wherein each pulsewidth of a head pulse and a succeeding pulse is designated to be 0.4times the recording period 1T and a pulse width of cooling pulse isdesignated to be 0.4 times the recording period 1T.

Succeedingly, the information recording medium 5 is loaded on the secondreproducing apparatus 41 shown in FIG. 34 equipped with the pickup 50having a wavelength λ of 405 nm and a numerical aperture NA of 0.85, anda land portion “L” is reproduced.

With respect to evaluation items, there is existed reflectivity andmodulated amplitude that is equal to “(I8H−I8L)/I8H”, which are obtainedfrom a total sum signal, reproduction laser power at limit ofdeterioration, reproduction error rate of record mark “M” obtained fromthe demodulator 54, and reproduction error rate of address informationrecorded in the auxiliary information area 200 that is obtained from theauxiliary information demodulator 56. The reproduction laser power atlimit of deterioration is obtained as follows: at first reproducing theinformation recording medium 5 by the reproduction laser power of 0.3mW, then measuring a laser power that deteriorates reproduction bygradually increasing reproduction laser power from 0.3 mW.

With respect to the reproduction laser power at limit of deteriorationand the reproduction error rate of record mark “M” and the error rate ofaddress information out of these evaluation items, they are judged bycomparing with a reference value and decided whether or not they areacceptable.

A reference value of reproduction laser power at limit of deteriorationis designated to be 0.35 mW. Each sample of the embodiments 1 through 7and comparative examples 1 and 2 is judged whether it is reproduced bythe laser power of more than 0.35 mW or less. Consequently, as shown inFIG. 39, a sample of which reproduction laser power at limit ofdeterioration is more than 0.35 mW is judged as acceptable and marked“Good”. On the contrary, another sample of which reproduction laserpower at limit of deterioration is less than 0.35 mW is judged asdefective and marked “Not”.

Further, with respect to a reference value of reproduction error rate ofreproduced signal, samples of which reproduction error rate is less than0.7×10⁻⁴ are judged as acceptable and marked “Good”, and other samplesof which reproduction error rate is more than 0.7×10⁻⁴ are judged asdefective and marked “Not”.

Furthermore, with respect to a reference value of address error rate,samples of which address error rate is less than 5% are judged asacceptable and marked “Good”, wherein 5% is a limit of restoring anaddress information by error correction. On the contrary, other samplesof which address error rate is more than 5% is judged as defective.

In addition thereto, each figure of reflectivity and modulated amplitudeand reproduction laser power at limit of deterioration, and eachjudgement of reproduction laser power at limit of deterioration, errorrate of reproduced signal, and address error rate with respect to theembodiments 1 through 7 and the comparative examples 1 and 2 isexhibited in FIG. 39.

As shown in FIG. 39, the embodiments 1 through 7, which are manufacturedby designating reflectivity to be within a range of 12% to 26%, areexcellent in every evaluation items, so that they can satisfyperformance as a total system.

Comparative Example 1

A sample of the comparative example 1 is manufactured by designatingreflectivity to be 11.0% and evaluated the same items as the samples ofthe embodiments 1 through 7. Result of the evaluation is shown in FIG.39. According to the evaluation, reproduction is deteriorated at 0.34mW. Therefore, it is concluded that the recording layer 123 is toosensitive. Consequently, an information recording medium of whichreflectivity is less than 11% is not suitable for a total system.

Comparative Example 2

A sample of the comparative example 2 is manufactured by designatingreflectivity to be 28.2% and evaluated the same items as the samples ofthe embodiments 1 through 7. Result of the evaluation is shown in FIG.39. In the case of the comparative example 2, reproduction is notdeteriorated. However, a reproduction error rate is excessively, so thatthe comparative example 2 is defective. The defect is caused by thatmodulated amplitude is too small as small as 0.389. In other words,sensitivity of the recording layer 123 is too low, so that it issupposed that recording in sufficient contrast is not conducted.Consequently, an information recording medium of which reflectivity ismore than 28% is not suitable for a total system.

According to the evaluation result of the embodiments 1 through 7 andthe comparative examples 1 and 2, reflectivity that is suitable forestablishing a total system is supposed to be within a range of 12% to26%. The 17PP modulation, where “d” is one and “k” is seven, is appliedfor the embodiments 1 through 7 and the comparative examples 1 and 2 asa recording signal. However, applying the “D4, 6” modulation, where “d”is one and “k” is nine, also obtains the same result.

Further, applying the “D8-15” modulation, where “d” is two and “k” isten, brings the same result as well.

Furthermore, in the embodiments 1 through 7, the auxiliary informationarea 200 is constituted by the frequency-shift keying modulation wave262. However, the phase-shift keying modulation wave 272 also brings thesame result. The amplitude-shift keying modulation wave 252 brings thesame result as well.

More, in the embodiments 1 through 7, the auxiliary information area 200and the reference clock area 300 is continuously formed withoutinterruption. However, in case that the auxiliary information area 200is connected to the reference clock area 300 with sandwiching a lineargroove having a length of 1 mm, the recording apparatus 90 can notconduct recording. Because, a reference clock can not be extracted fromthe linear groove, so that revolution servo can not be applied to theturntable 53.

Moreover, in the embodiments 1 through 7, the auxiliary information area200 and the reference clock area 300 is formed on a land portion “L”. Incase that the auxiliary information area 200 and the reference clockarea 300 is formed on a groove portion “G”, the recording apparatus 90can not conduct recording. Because, the recording light 89 of therecording apparatus 90 is focused on the land portion “L”, so that areproduced signal from the reference clock area 300 is interfered by areference clock signal twice. Consequently, an extremely unstable clockcan only be extracted.

By designating reflectivity to be more than 5%, particularly, to bewithin a range of 12% to 26% as mentioned above, the informationrecording mediums 1 through 5 according to the present invention cancompensate the problem of adding a particular noise inherent in asemiconductor laser of gallium nitride system compound utilized for thefirst and second reproducing apparatuses 40 and 41 to a reproducedsignal.

A method of regulating modulated amplitude to be within a predeterminedrange as a second method of compensating the problem of adding aparticular noise inherent in a semiconductor laser of gallium nitridesystem compound to a reproduced signal is explained next.

By changing each material and each layer thickness of the reflectivelayer 121, the first protective layer 122, the recording layer 123 andthe second protective layer 124 of the information recording medium 5according to the fifth embodiment of the present invention, severalsamples of information recording mediums are manufactured. These samplesare reproduced by the first reproducing apparatus 40 in which asemiconductor laser of gallium nitride system compound having a laserRIN of −125 dB/Hz is adopted as the light emitting element 50 a, andevaluated with respect to a relation between modulated amplitude and anerror rate of reproduced signal. Recording hereupon is conducted by therecording apparatus 90 under most ideal recording conditions so as todecrease an error rate to the utmost limit.

Reproduction modulated amplitude is an output of reproduced signal. Incase that the recording layer 123 is constituted by a phase changematerial, modulated amplitude is an index correlating to reflectivitycontrast between crystal and amorphous. More specifically, the modulatedamplitude is obtained by recording a modulation signal of the (d, k)code in the information recording medium 5 by the recording apparatus90.

The information recording medium 5 is loaded on the second reproducingapparatus 41 in flat, that is, without being inclined and a recordedsignal is reproduced, and then a reproduced signal in DC systemoutputted from the pickup 50 is connected to a oscilloscope.Consequently, modulation amplitude is obtained from a signal (k+1)having the maximum mark length that is utilized for the (d, k) codingmethod. In the case of the “8-16” modulation method that is utilized forthe DVD system, for example, the maximum mark length is 14T. Therefore,by measuring I14L and I14H as specified in the JIS Standard X6241/1997,modulated amplitude, that is, (I14H−I14L)/I14H is calculated.

On the other hand, in the case of the 17PP modulation method, themaximum mark length is 8T. Therefore, by measuring I8L and I8H,modulated amplitude, that is, (I8H−I18L)/I18H is calculated.

Further, in the case of the “D4, 6” modulation method, the maximum marklength (k+1) is 10T. Therefore, by measuring I10L and I10H, modulatedamplitude, that is, (I10H−I10L)/I10H is calculated.

Furthermore, an error rate is obtained by measuring a reproduced signalobtained through the demodulator 54.

Result of measuring modulated amplitude and an error rate by the firstreproducing apparatus 40 after recording a signal modulated by the 17PPmodulation method by the recording apparatus 90 is shown in FIG. 40.

FIG. 40 is a graph exhibiting a relation between modulated amplitude anderror rate. As shown in FIG. 40, there is existed an apparentrelationship between modulated amplitude and error rate. It is apparentthat an error rate drastically increases in accordance with modulatedamplitude that decreases. In case that a practical error rate is definedas 3×10⁻⁴ that is the figure specified by the several standards such asthe DVD Standard, necessary modulated amplitude is more than 0.34.

Further, an information recording medium 5 may warp by temperaturechange in the surrounding of use. Consequently, with assuming that theinformation recording medium 5 inclines by the order of 0.7 degree thatis the same angle as a DVD disc, an error rate increases more than comaaberration caused compositively by conditions such that a wavelength λis within a range of 350 nm to 450 nm, a numerical aperture NA is withina range of 0.75 to 0.9, and a thickness of the light transmitting layer11 is within a range of 0.07 mm to 0.12 mm.

When the information recording medium 5 is inclined by 0.7 degree, it isfound by an actual measurement that the error rate of 3×10⁻⁴ isequivalent to 0.7×10⁻⁴ when the incline is zero degree. In other words,the error rate of 0.7×10⁻⁴ is essential in consideration of inclinewhile actual use.

Accordingly, it is found that practical modulated amplitude is more than0.4.

As mentioned above, in consideration of the phenomenon of adding noisewhen a semiconductor laser of gallium nitride system compound is usedfor a light emitting element, an error rate can be suppressed to thesame level as the DVD Standard and becomes a practical level if aninformation recording medium 5 is constituted such that modulatedamplitude is more than 0.4.

In addition thereto, with respect to the correlation between modulatedamplitude and error rate as shown in FIG. 40, it is experimentallyunderstood that almost similar results are obtained from any modulationmethods applied for the above-mentioned (d, k) code. A signal output isalmost saturated by any of these modulation methods when the maximummark length exceeds 6T although a maximum mark length (k+1) may vary bythe modulation method. Consequently, a value of modulated amplitudeobtained from an information recording medium 1 recorded by the 17PPmodulation method, for example, is the same as that obtained from theinformation recording medium 1 recorded by the “D4, 6” modulationmethod. The same results are obtained although the information recordingmedium 1 is replaced with an information recording medium 5.

Further details are explained as embodiments 8 through 12 next. Inaddition, samples of comparative examples 3 through 5 are alsomanufactured for the purpose of comparison.

Embodiment 8

A sample of an embodiment 8 is manufactured as a phase-change recordingtype information recording medium 5. A polycarbonate plate having athickness of 1.1 mm is utilized for a substrate 13. A reflective layer121, a first protective layer 122, a recording layer 123, and a secondprotective layer 124 is constituted by Ag₉₈Pd₁Cu₁, ZnS—SiO₂ (80:20 atmol %), Ag—In—Sb—Te, and ZnS—SiO₂ (80:20 at mol %) respectively.Finally, a polycarbonate plate having a thickness of 0.10 mm islaminated on the second protective layer 124 as a light transmittinglayer 11.

The sample of the embodiments 8 (hereinafter simply referred to asembodiment 8) is manufactured as an information recording medium 5.

An auxiliary information area 200 and a reference clock area 300 isformed continuously on a land portion “L” of the information recordingmedium 5 of the embodiment 8 without being interrupted. The auxiliaryinformation area 200 is composed of a frequency-shift keying modulationwave 262 of which fundamental wave is a sinusoidal wave (or a cosinewave), wherein a phase difference between a higher frequency section anda lower frequency section is “2π±(π/2.5)”.

Further, a phase is selected so as to be that the waveform continues ata point where a frequency changes over from higher to lower or viceversa.

Furthermore, the auxiliary information area 200 is recordedgeometrically on a sidewall as a wobbling groove.

In addition thereto, a single-frequency wave 350 of which fundamentalwave is a sinusoidal wave (or a cosine wave) is recorded geometricallyon a sidewall as a wobbling groove.

The embodiment 8 is designed for recording or reproducing by using apickup installed with optical elements of which wavelength λ is 405 nmand an NA is 0.85. A pitch “P” between land portions “L” of theembodiment 8 is 0.32 μm.

Further, the reflective layer 121 and the recording layer 123 is formedby the DC sputtering process, and the first and second protective layers122 and 124 are formed by the AC sputtering process in an atmosphere ofargon gas of 5 mTorr.

Furthermore, a vacuum chamber used for sputtering process issufficiently exhausted as low as less than 1×10⁻⁶ Torr.

More, the embodiment 8 is initialized by irradiating a laser beam on therecording layer 123 through the light transmitting layer 11, and therecording layer 123 is phase-changed from an amorphous state in lowerreflectivity to a crystalline state in higher reflectivity.

The embodiment 8 is loaded on the recording apparatus 90 equipped with apickup installed with optical elements of which wavelength λ is 405 nmand an NA is 0.85. A recording signal is recorded on a land portion “L”with a modulation signal of which minimum mark length that is equal to2T is designated to be 0.149 μm by the 17PP modulation method.

Further, a differential signal reproduced from the reference clock area300 of the embodiment 8 is transmitted to the reference clockdemodulator 57, and then revolution of the turntable 53 is controlled bythe obtained reference clock. By controlling the turntable 53 asmentioned above, a record mark “M” having a desired length is conductedto be recorded accurately.

With respect to a recording condition, a recording peak power is 6.0 mW,a bias power is 2.6 mW, a bottom power between multi-pulses and a bottompower of a cooling pulse is 0.1 mW respectively, and a linear velocityis 5.3 m/s.

Furthermore, the recording is conducted by a signal, which istransformed into a so-called multi-pulse by the waveform converter 83. A3-level power modulation method is adopted, wherein each pulse width ofa head pulse and a succeeding pulse is designated to be 0.4 times therecording period 1T and a pulse width of cooling pulse is designated tobe 0.4 times the recording period 1T.

Succeedingly, the embodiment 8 is loaded on the second reproducingapparatus 41 equipped with the pickup 50 having a wavelength λ of 405 nmand a numerical aperture NA of 0.85, and then a land portion “L” isreproduced.

With respect to evaluation items, there is existed modulated amplitudethat is equal to “(I8H−I8L)/I8H” and obtained from a total sum signal,reproduction laser power at limit of deterioration, reproduction errorrate of record mark “M” obtained from the demodulator 54, andreproduction error rate of address information recorded in the auxiliaryinformation area 200 that is obtained from the auxiliary informationdemodulator 56.

A signal of which modulated amplitude that is equal to “(I8H−I8L)/I8H”is 0.52 is reproduced from a total sum signal. Succeedingly, anexcellent error rate as low as 2×10⁻⁵ is obtained from a reproducedsignal outputted from the demodulator 56. Consequently, data that do notcome into question in practical application are extracted.

Further, an error rate of address information obtained from theauxiliary information demodulator 56 is the order of 1% in a recordedsection, so that address data is restored excellently.

Furthermore, in case that an error rate of address information is lessthan 5% when reproducing after recorded in the recording layer 123,almost errorless data can be restored by a error correction process.Consequently, less than 5% is suitable for the error rate of addressinformation.

Embodiment 9

A sample of embodiment 9 (hereinafter simply referred to as embodiment9) is identical to the embodiment 8 except for the modulation method. Incase of the embodiment 9, a recording signal is modulated by the “D4, 6”modulation method and the minimum mark length that is equal to 2T is0.154 μm. The embodiment 9 is recorded and reproduced as the same manneras the embodiment 8. A signal of which modulated amplitude that is equalto “(I10H−I10L)/I10H” is 0.60 is reproduced when reproducing a landportion “L”. Succeedingly, an excellent error rate as low as 8×10⁻⁶ isobtained from a reproduced signal. Consequently, data that do not comeinto question in practical application are extracted.

Further, an error rate of address information is the order of 1% in arecorded section, so that address data are restored excellently.

Embodiment 10

A sample of embodiment 10 (hereinafter simply referred to as embodiment10) is identical to the embodiment 8 except for the modulation method.In case of the embodiment 10, a recording signal is modulated by the“D8-15” modulation method and the minimum mark length that is equal to3T is 0.185 μm. The embodiment 10 is recorded and reproduced as the samemanner as the embodiment 8. A signal of which modulated amplitude thatis equal to “(I12H−I12L)/I12H” is 0.63 is reproduced when reproducing aland portion “L”. Succeedingly, an excellent error rate as low as 4×10⁻⁶is obtained from a reproduced signal. Consequently, data that do notcome into question in practical application are extracted.

Further, an error rate of address information is the order of 1% in arecorded section, so that address data are restored excellently.

Embodiment 11

A sample of embodiment 11 (hereinafter simply referred to as embodiment11) is identical to the embodiment 8 except for the modulation methodand recording of auxiliary information. In case of the embodiment 11,auxiliary information data are recorded in a wobbling shape by thephase-shift keying modulation wave 272.

Further, a recording signal is modulated by the 17PP modulation methodand the minimum mark length that is equal to 2T is 0.149 μm.

The embodiment 11 is recorded and reproduced as the same manner as theembodiment 8. A signal of which modulated amplitude that is equal to“(I8H−I8L)/I8H” is 0.60 is reproduced when reproducing a land portion“L”. Succeedingly, an excellent error rate as low as 2×10⁻⁵ is obtainedfrom a reproduced signal. Consequently, data that do not come intoquestion in practical application are extracted.

Furthermore, an error rate of address information is the order of 0.1%in a recorded section, so that address data are restored excellently.

Embodiment 12

A sample of embodiment 12 (hereinafter simply referred to as embodiment12) is identical to the embodiment 8 except for the modulation method.In case of the embodiment 12, auxiliary information data are processedthrough the base-band modulation by the Manchester coding method.

Further, the auxiliary information data processed through the base-bandmodulation are modulated to be the frequency-shift keying modulationwave 262 shown in FIG. 22, wherein a phase relation between a higherfrequency section and a lower frequency section is 2π±(π/2.5).

Furthermore, the embodiment 12 is recorded with a wobbling shape by thefrequency-shift keying modulation method, wherein a phase is selectedsuch that a waveform continues at a point where a frequency changesover.

More, a recording signal is modulated by the “D4, 6” modulation methodand the minimum mark length that is equal to 2T is 0.154 μm.

The embodiment 12 is recorded and reproduced as the same manner as theembodiment 8. A signal of which modulated amplitude that is equal to(I10H−I10L)/I10H is 0.60 can be reproduced when reproducing a landportion “L”. Succeedingly, an excellent error rate as low as 8×10⁻⁶ isobtained from a reproduced signal. Consequently, data that do not comeinto question in practical application can be extracted.

Moreover, an error rate of address information is the order of 1% in arecorded section, so that address data are restored excellently.

Comparative Example 3

A sample of comparative example 3 (hereinafter simply referred to ascomparative example 3) is identical to the embodiment 8 except forrecording that is conducted to a groove portion “G” of the informationrecording medium 5 according to the embodiment 1. A signal havingmodulated amplitude of 0.38 is reproduced by reproducing a grooveportion “G”. Succeedingly, an error rate of 4×10⁻³ is obtained from areproduced signal. Consequently, data, which contain many defective anderratic portions that are impossible to correct, are extracted.

Further, address data are completely disordered, and extracting data isimpossible.

Comparative Example 4

A sample of comparative example 4 (hereinafter simply referred to ascomparative example 4) is identical to the embodiment 8 except for thethickness of the light transmitting layer 11. In case of the comparativeexample 4, a thickness of the light transmitting layer 11 is 0.06 mm. Asignal having modulated amplitude of 0.46 is reproduced. However, an eyepattern is obscure. Succeedingly, an error rate of 6×10⁻³ is obtainedfrom a reproduced signal. Consequently, data, which contain manydefective and erratic portions that are impossible to correct, areextracted.

Further, an error rate of address information is 10% in a recordedsection, so that address data are defective and contain many erraticportions that are impossible to correct.

Furthermore, the comparative example 4 is easily scratched by a scratchtest such that the objective lens 50 b is forced to contact with thecomparative example 4 and to slide. Consequently, the comparativeexample 4 is not suitable for an information recording medium.

Comparative Example 5

A sample of comparative example 5 (hereinafter simply referred to ascomparative example 5) is identical to the embodiment 8 except for thethickness of the light transmitting layer 11. In case of the comparativeexample 5, a thickness of the light transmitting layer 11 is 0.13 mm. Asignal having modulated amplitude of 0.38 is reproduced. However, an eyepattern is obscure. Succeedingly, an error rate of 9×10⁻³ is obtainedfrom a reproduced signal. Consequently, data, which contain manydefective and erratic portions that are impossible to correct, areextracted.

Further, an error rate of address information is 10% in a recordedsection, so that address data are defective and contain many erraticportions that are impossible to correct.

Accordingly, in consideration of the result of evaluation beingconducted to the embodiments 1 through 7 and the comparative examples 1and 2, which are summarized in FIG. 40, and the embodiments 8 through 12and the comparative examples 3 through 5, it is concluded that a rangeof modulated amplitude that is suitable for establishing a total systemis more than 0.4.

Details of the information recording mediums 1 through 5, the first andsecond reproducing apparatuses 40 and 41, and the recording apparatus 90according to the present invention are explained hereinbefore.

While the invention has been described above with reference to specificembodiment thereof, it is apparent that many changes, modification andvariations in the arrangement of equipment and devices can be madewithout departing from the invention concept disclosed herein. Forexample, in the case of the information recording medium 1, themicroscopic pattern 20 is constituted by only one layer. However, theinformation recording medium 1 can be expanded to an informationrecording medium in which one set of layers constituted by the recordinglayer 12 and the light transmitting layer 13 is repeatedly laminated aplurality of times and a plurality of layers of microscopic patternssuch as two layers, three layers and four layers is formed.

Further, with respect to the first and second reproducing apparatuses 40and 41 and the recording apparatus 90, the present invention providesnot only the apparatuses themselves but also their operations.

Furthermore, the present invention provides the reproducing method andthe recording method that is conducted by replacing each operation ofapparatuses with each step of procedures of the operations respectively.

More, the present invention provides computer programs that execute eachstep of the reproducing method and the recording method.

Moreover, the preset invention provides a recording and reproducingapparatus that combines the first or second reproducing apparatus andthe recording apparatus, and provides a recording and reproducing methodthat combines the reproducing method and the recording method.

In addition thereto, the present invention provides a system that isconstituted by combining the information recording medium, thereproducing apparatus, the recording apparatus, the reproducing method,and the recording method totally.

According to the present invention, as mentioned above, there isprovided an information recording medium that is composed of at least asubstrate having a microscopic pattern, which is constituted by acontinuous substance of approximately parallel grooves formed with agroove portion and a land portion alternately, a recording layer formedon the microscopic pattern, and a light transmitting layer having athickness of 0.07 mm to 0.12 mm, which is formed on the recording layer.

Further, with defining that a pitch between the groove portions or theland portions is “P” and a wavelength of reproducing light is λ and anumerical aperture of an objective lens is NA, the microscopic patternis formed with satisfying a relation of P≦λ/NA.

Furthermore, recording is conducted in accordance with either one ofreflectivity difference and phase difference caused by recording ineither the land portion or the groove portion so as to be more than 5%for reflectivity while the wavelength λ is within the range of 350 nm to450 nm and the numerical aperture NA is within the range of 0.75 to 0.9.

Accordingly, making recording density of the information recordingmedium higher can be realized as well as reducing cross erase.

In addition thereto, an error rate can be suppressed down to a practicallevel. In other words, by combining with a reproducing apparatus, arecording apparatus, a reproducing method, and a recording method, atotal system can be established.

Particularly, designating reflectivity to be within a range of 12% to26% can establish a total system in combination with a reproducingapparatus and a recording apparatus.

Further, according to the present invention, recording is conducted inaccordance with either one of reflectivity difference and phasedifference caused by recording in either the land portion or the grooveportion so as to be more than 0.4 for modulated amplitude. Consequently,making recording density of the information recording medium higher canbe realized as well as reducing cross erase.

Furthermore, an error rate can be suppressed down to a practical level.In other words, by combining with a reproducing apparatus, a recordingapparatus, a reproducing method, and a recording method, a total systemcan be established.

An auxiliary information such as address data is recorded geometricallyin a part of microscopic pattern by the amplitude-shift keyingmodulation method. Therefore, recorded data can be demodulated evenunder low C/N condition.

Further, an auxiliary information such as address data is recordedgeometrically in a part of microscopic pattern by the frequency-shiftkeying modulation method. Therefore, recorded data can be demodulated bya simplified circuitry. Particularly, by utilizing a frequency-shiftkeying modulation in which a phase is selected such that a wavecontinues at a point of changing a frequency, a reproduction envelope ismade constant and stable reproduction is enabled.

Furthermore, an auxiliary information such as address data is recordedgeometrically in a part of microscopic pattern by the phase-shift keyingmodulation method. Therefore, recorded data can be reproduced even underlow C/N condition by demodulating the modulated data by the synchronousdetection method.

Particularly, phase difference between a higher frequency section and alower frequency section, which constitute a frequency-shift keyingmodulation wave, is set to ±π/2.5, excellent signal demodulation isenabled by the synchronous detection method.

Furthermore, a reference clock is recorded in succession to an auxiliaryinformation in a part of microscopic pattern, so that controllingrevolution of a reproducing apparatus and a recording apparatus isenabled. Recording by stabilized length of record mark can be conducted,particularly when recording.

It should be understood that many modifications and adaptations of theinvention will become apparent to those skilled in the art and it isintended to encompass such obvious modifications and changes in thescope of the claims appended hereto.

What is claimed is:
 1. An information recording medium comprising: asubstrate having a first microscopic pattern corresponding to arecording and reproducing area and a second microscopic patterncorresponding to a read-only area, each microscopic pattern including acontinuous substrate of grooves formed with a groove portion and a landportion alternately; a recording layer formed on the microscopic patternfor recording information; and a light transmitting layer formed on therecording layer, wherein the land portion corresponding to the recordingand reproducing area is formed with wobbling so as to be parallel witheach other for both sidewalls of the land portion, and wherein auxiliaryinformation, based on data used supplementally when recording theinformation and a reference clock based on a clock used for controllinga recording speed when recording the information, are recordedalternately and continuously in the recording and reproducing area, andwherein the auxiliary information is recorded by a frequency-shiftkeying modulation wave having two different frequencies, and wherein thereference clock is composed of a single frequency, and further whereinthe single frequency coincides with either one frequency of the twodifferent frequencies, further wherein the read-only area is allocatedin an inner circumference side of the recording and reproducing area inthe information recording medium, and is formed by a bar code, andwherein an identification information of the information recordingmedium is recorded in the read-only area.
 2. A reproducing apparatus forreproducing a recording layer of an information recording mediumcomprising: a substrate having a first microscopic pattern correspondingto a recording and reproducing area, and a second microscopic patterncorresponding to a read-only area, each microscopic pattern including acontinuous substrate of grooves formed with a groove portion and a landportion alternately; the recording layer formed on the microscopicpattern for recording information; and a light transmitting layer formedon the recording layer, wherein the land portion corresponding to therecording and reproducing area is formed with wobbling so as to beparallel with each other for both sidewalls of the land portion, andwherein auxiliary information, based on data used supplementally whenrecording the information and a reference clock based on a clock usedfor controlling a recording speed when recording the information, arerecorded alternately and continuously in the recording and reproducingarea, and wherein the auxiliary information is recorded by afrequency-shift keying modulation wave having two different frequencies,and wherein the reference clock is composed of a single frequency, andfurther wherein the single frequency coincides with either one frequencyof the two different frequencies, further wherein the read-only area isallocated in an inner circumference side of the recording andreproducing area in the information recording medium, and is formed by abar code, and wherein an identification information of the informationrecording medium is recorded in the read-only area, and the reproducingapparatus comprising: a light emitting element for emitting reproducinglight having a wavelength λ of 350 nm to 450 nm and a noise of less thanRIN (Relative Intensity Noise) −125 dB/Hz; a reproducing means equippedwith an objective lens having a numerical aperture NA of 0.75 to 0.9;and a control means for controlling the reproducing means to irradiatethe reproducing light only on the land portion for reproducing, whereinthe reproducing means reproduces both the recording and reproducing areaand the read-only area.